allergy

What is allergy

An allergy is a reaction by your immune system to something (called allergens) that does not bother most other people. When your body is exposed to allergens it releases histamine, a chemical. Histamine makes you sneeze, makes your nose run, and makes you eyes and skin itch and swell up. In a way, it is trying to get you to sneeze out or scratch away the allergen. In affected people, allergies can trigger conditions such as asthma and hay fever, skin conditions such as eczema, and eye conditions such as conjunctivitis.

People who have allergies often are sensitive to more than one thing. Genes and the environment probably both play a role.

Substances that often cause allergic reactions are:

  • Grass and tree pollen – an allergy to these is known as hay fever (allergic rhinitis)
  • Dust mites
  • Mold spores – these can release small particles into the air that you can breathe in
  • Pet dander (tiny flakes of skin or hair)
  • Food – particularly nuts, fruit, shellfish, eggs and cow’s milk
  • Insect bites and stings
  • Medicine – including ibuprofen, aspirin, and certain antibiotics
  • Household chemicals – including those in detergents and hair dyes
  • Latex – used to make some gloves and condoms

Most of these allergens are generally harmless to people who aren’t allergic to them.

Normally, your immune system fights germs. It is your body’s defense system. Sometimes your immune system becomes hypersensitive to chemicals from foods (peanuts, shellfish, nuts, eggs, wheat); animals (dogs, cats); and other materials (grasses, dust, dustmites, medicines). This causes allergic reactions. For most people, the allergic reaction is hay fever (runny nose, sneezing, and itchy eyes), hives (a bumpy skin rash), itching, swelling or asthma. In some people this reaction is severe and causes anaphylaxis. Anaphylaxis is a severe reaction that can be life-threatening needing immediate injection with adrenaline from an epi-pen.

Allergies can range from minor to severe. Doctors use skin and blood tests to diagnose allergies.

Allergy testing is important in managing allergies, as testing indicates what you are allergic to. Testing will also help your doctor advise you on the best ways to avoid these allergens.

Treatments include medicines, allergy shots, and avoiding the substances that cause the reactions.

What causes allergies?

Allergies occur when the body’s immune system reacts to a particular substance as though it’s harmful.

It’s not clear why this happens, but most people affected have a family history of allergies or have closely related conditions such as asthma or eczema.

The number of people with allergies is increasing every year. The reasons for this are not understood, but one of the main theories is it’s the result of living in a cleaner, germ-free environment, which reduces the number of germs our immune system has to deal with.

It’s thought this may cause it to overreact when it comes into contact with harmless substances.

Is it an allergy, sensitivity or intolerance?

  • allergy – a reaction produced by the body’s immune system when exposed to a normally harmless substance
  • sensitivity – the exaggeration of the normal effects of a substance; for example, the caffeine in a cup of coffee may cause extreme symptoms, such as palpitations and trembling
  • intolerance – where a substance causes unpleasant symptoms, such as diarrhoea, but doesn’t involve the immune system; people with an intolerance to certain foods can typically eat a small amount without having any problems

Allergy symptoms

Symptoms of an allergic reaction usually develop within a few minutes of being exposed to something you’re allergic to, although occasionally they can develop gradually over a few hours.

Although allergic reactions can be a nuisance and hamper your normal activities, most are mild. Very occasionally, a severe reaction called anaphylaxis can occur.

Main allergy symptoms

Common symptoms of an allergic reaction include:

  • sneezing and an itchy, runny or blocked nose (allergic rhinitis)
  • itchy, red, watering eyes (conjunctivitis)
  • wheezing, chest tightness, shortness of breath and a cough
  • a raised, itchy, red rash (hives)
  • swollen lips, tongue, eyes or face
  • tummy pain, feeling sick, vomiting or diarrhoea
  • dry, red and cracked skin

The symptoms vary depending on what you’re allergic to and how you come into contact with it. For example, you may have a runny nose if exposed to pollen, develop a rash if you have a skin allergy, or feel sick if you eat something you’re allergic to.

Severe allergic reaction (anaphylaxis)

In rare cases, an allergy can lead to a severe allergic reaction, called anaphylaxis or anaphylactic shock, which can be life-threatening.

This affects the whole body and usually develops within minutes of exposure to something you’re allergic to.

Symptoms of severe allergy (anaphylaxis) may include:

  • trouble breathing or noisy breathing
  • difficulty talking more than a few words and/or hoarse voice
  • wheeze
  • cough
  • swelling and tightness of the throat
  • collapse
  • light-headedness or dizziness
  • diarrhea
  • tingling in the hands, feet, lips or scalp
  • swelling of tongue
  • pale and floppy (in young children)

A severe allergic reaction (anaphylaxis) is a medical emergency. Call your local emergency immediately. Lay the person down. If they have an adrenaline injector and you are able to administer it, do so.

Figure 1. Anaphylaxis Emergency Action Plan

Anaphylaxis-Emergency-Action-Plan

Hay fever (allergic rhinitis)

Hay fever is the common term for ‘allergic rhinitis’. It’s caused by an allergic response to outdoor or indoor allergens such as pollen, dust mites, fungal spores, animal fur or occupational sources.

Allergens are most commonly proteins or enzymes that can cause the nose, eyes, throat and sinuses (small air-filled cavities behind your cheekbones and forehead) to become swollen, irritated and inflamed.

When you have an allergic reaction, your body overreacts to something that would be harmless for most people. Your immune system (the body’s natural defence system) starts to respond as if it’s under threat, and releases a number of chemicals including histamine. This results in swelling and inflammation.

Hay fever symptoms include:

  • Sneezing
  • Runny nose and nasal congestion
  • Watery, itchy, red eyes (allergic conjunctivitis)
  • Cough
  • Itchy nose, roof of mouth or throat
  • Swollen, blue-colored skin under the eyes (allergic shiners)
  • Postnasal drip
  • Fatigue

Hay fever usually begins in childhood or during the teenage years, but you can acquire it at any age. It affects nearly to 1 in 5 Australians at some point in their life, and is more likely to occur if there is a family history of allergies – particularly asthma or eczema. In fact, hay fever and asthma share many of their risk and trigger factors including a genetic predisposition to develop allergic reactions.

Most people are able to relieve their symptoms with treatment – at least to a certain extent.

What causes hay fever?

The most common hay fever causes and triggers are discussed below; however, it’s important to note that it’s not caused by a food allergy.

House dust

House dust contains numerous organic and inorganic compounds such as house dust mites, hair, smoke, dirt, fibers, mold spores, pollen grains, insects, mammalian dander (small scales from the skin or hair of pets), as well as secreta (such as saliva) and excreta (such as feces) from insects, mites and pets.

Of all of these compounds, house dust mites are the most widespread and are commonly found in mattresses, bed bases, pillows, carpets and upholstered furniture. Although they are present all year round, their numbers usually peak during humid periods.

Pets

Household pets, especially cats and dogs, are an important source of domestic allergens which are found in the animal’s fur and in house dust. The allergens can remain airborne for long periods of time, and people who are ‘allergic’ to these animals may also react to allergens from other animals such as horses, rabbits and guinea pigs.

Pollens

Pollens are produced by trees, grasses, flowers and other plants to fertilize the female flower in order to reproduce that plant species. The type and number of pollens vary according to an area’s vegetation, geography, temperature and climate.

Most of the pollen that causes allergies is produced by airborne pollen from introduced northern hemisphere grasses, trees and weeds such as Pellitory weed, Paterson’s Curse, Ragweed and Parthenium.

  • Tree pollen, which is common in early spring.
  • Grass pollen, which is common in late spring and summer.
  • Ragweed pollen, which is common in fall.

Fungal allergens

Fungi, such as mold can release large amounts of allergenic spores into the indoor and outdoor environments. Outdoor molds can be present in all conditions, with seasonal peaks in hot and humid conditions, while indoor molds are associated with dampness. They are particularly plentiful in bathrooms and kitchens.
Occupational exposures

Occupational irritants can cause and worsen the symptoms of hay fever. They include different forms such as fumes, dust, vapors and gases, or different types such as chlorine or wood dust.

Common allergens in the workplace can include natural latex rubber (made using a water-soluble protein obtained from a particular rubber tree), bakery allergens such as wheat, enzymes and mites that may be in stored cereal, while people working in fish/seafood processing plants can become sensitized from breathing fish/crustacean proteins in. Scientists in cleaning product companies can also sensitize to the enzymes contained in products such as washing powder, while laboratory workers can sensitize to rats and mice.

The correct treatments can be effective in reducing your symptoms. You should seek advice from your doctor or a pharmacist about which medicines or treatments will relieve your particular symptoms based on their severity.

Risk factors for developing hay fever

The following can increase your risk of developing hay fever:

  • Having other allergies or asthma
  • Having atopic dermatitis (eczema)
  • Having a blood relative (such as a parent or sibling) with allergies or asthma
  • Living or working in an environment that constantly exposes you to allergens — such as animal dander
  • Having a mother who smoked during your first year of life

Complications of hay fever

Problems that may be associated with hay fever include:

  • Reduced quality of life. Hay fever can interfere with your enjoyment of activities and cause you to be less productive. For many people, hay fever symptoms lead to absences from work or school.
  • Poor sleep. Hay fever symptoms can keep you awake or make it hard to stay asleep, which can lead to fatigue and a general feeling of being unwell (malaise).
  • Worsening asthma. Hay fever can worsen signs and symptoms of asthma, such as coughing and wheezing.
  • Sinusitis. Prolonged sinus congestion due to hay fever may increase your susceptibility to sinusitis — an infection or inflammation of the membrane that lines the sinuses.
  • Ear infection. In children, hay fever often is a factor in middle ear infection (otitis media).

Prevention of hay fever

Reducing your exposure to the substances that trigger your hay fever should ease your symptoms. It is therefore important to try and find out what the allergen is.

However, there are some general preventative steps you can take that might help.

If your allergen is pollen:

  • Avoid cutting grass, playing or walking in grassy areas, and camping. If you have to do so, wear a mask or take a non-drowsy antihistamine
  • Wear wraparound sunglasses to stop pollen getting into your eyes when you are outdoors.
  • Change your clothes and take a shower after being outdoors to remove the pollen on your body.
  • Keep the windows closed at home and in the car, and use recirculating air-conditioning in the car.
  • Try to stay indoors when the pollen index (or count) is high, for example before midday, during windy days or after a thunderstorm. You can find the pollen index via online weather information services such as Weatherzone (www.weatherzone.com.au), or the pollen forecast.
  • If possible, avoid drying clothes outside. This will help prevent bringing pollen into your house.
  • Consider planting a low-allergen garden around your home and remove any weeds or trees if you are sensitive to them.

Preventative steps for most allergens include:

  • Damp dust regularly because dusting with a wet cloth, rather than a dry one, will collect the dust and stop any pollen from being spread around.
  • Keep pets out of the house when your symptoms flare up. If your pet does come inside, wash them regularly to remove any allergens from their fur.
  • Don’t smoke or let other people smoke in your house. Smoking and breathing in other people’s smoke will irritate the lining of your nose, eyes, throat and airways, and can make your symptoms worse.
  • If your hay fever is due to allergens in your workplace, you should advise your employer of this fact so that you can work together to reduce your exposure.

Hay fever diagnosis

Your doctor will perform a physical examination, take a medical history and possibly recommend one or both of the following tests:

  • Skin prick test. You’re watched for an allergic reaction after small amounts of material that can trigger allergies are pricked into the skin of your arm or upper back. If you’re allergic, you develop a raised bump (hive) at the site of that allergen. Allergy specialists usually are best equipped to perform allergy skin tests.
  • Allergy blood test. A blood sample is sent to a lab to measure your immune system’s response to a specific allergen. Also called the radioallergosorbent test (RAST), this test measures the amount of allergy-causing antibodies in your bloodstream, known as immunoglobulin E (IgE) antibodies.

Treatment of hay fever

It’s best to limit your exposure to substances that cause your hay fever as much as possible. If your hay fever isn’t too severe, over-the-counter medications may be enough to relieve symptoms. For worse symptoms, you may need prescription medications.

Many people get the best relief from a combination of allergy medications. You might need to try a few before you find what works best.

If your child has hay fever, talk with your doctor about treatment. Not all medications are approved for use in children. Read labels carefully.

Medications for hay fever include:

Nasal corticosteroids. These prescription nasal sprays help prevent and treat the nasal inflammation, nasal itching and runny nose caused by hay fever. For many people they’re the most effective hay fever medications, and they’re often the first type of medication prescribed.

Examples include fluticasone propionate (Flonase), triamcinolone (Nasacort AQ), mometasone (Nasonex) and budesonide (Rhinocort Aqua). An over-the-counter version (Flonase Allergy Relief) recently became available. A newer prescription nasal spray combines an antihistamine with a steroid (Dymista).

Nasal corticosteroids are a safe, long-term treatment for most people. Side effects can include an unpleasant smell or taste and nose irritation. Steroid side effects are rare.

Antihistamines. These preparations are usually given as pills. However, there are also antihistamine nasal sprays and eye drops. Antihistamines can help with itching, sneezing and a runny nose but have less effect on congestion. They work by blocking histamine, a symptom-causing chemical released by your immune system during an allergic reaction.

Over-the-counter examples include loratadine (Claritin, Alavert), cetirizine (Zyrtec Allergy) and fexofenadine (Allegra Allergy). The prescription antihistamine nasal sprays azelastine (Astelin, Astepro) and olopatadine (Patanase) can relieve nasal symptoms. Antihistamine eye drops help relieve eye itchiness and eye irritation caused by hay fever.

Decongestants. These medications are available in over-the-counter and prescription liquids, tablets and nasal sprays. Over-the-counter oral decongestants include pseudoephedrine (Sudafed, Afrinol, others). Nasal sprays include phenylephrine (Neo-Synephrine) and oxymetazoline (Afrin).

Oral decongestants can cause a number of side effects, including increased blood pressure, insomnia, irritability and headache. Don’t use a decongestant nasal spray for more than two or three days at a time because it can actually worsen symptoms when used continuously (rebound congestion).
Cromolyn sodium. This is available as an over-the-counter nasal spray that must be used several times a day. It’s also available in eye drop form with a prescription (Crolom). It helps relieve hay fever symptoms by preventing the release of histamine. Most effective when you start using before you have symptoms, Cromolyn sodium doesn’t have serious side effects.

Leukotriene modifier. Montelukast (Singulair) is a prescription tablet taken to block the action of leukotrienes — immune system chemicals that cause allergy symptoms such as excess mucus production. It’s especially effective in treating allergy-induced asthma. It’s often used when nasal sprays can’t be tolerated or when you have mild asthma.

Montelukast can cause headaches. In rare cases, it has been linked to psychological reactions such as agitation, aggression, hallucinations, depression and suicidal thinking. Seek medical advice right away for any unusual psychological reaction.

Nasal ipratropium. Available in a prescription nasal spray, ipratropium (Atrovent) helps relieve severe runny nose by preventing the glands in your nose from producing excess fluid. It’s not effective for treating congestion, sneezing or postnasal drip.

Mild side effects include nasal dryness, nosebleeds and sore throat. Rarely, it can cause more-severe side effects, such as blurred vision, dizziness and difficult urination. The drug is not recommended for people with glaucoma or men with an enlarged prostate.

Oral corticosteroids. Corticosteroid pills such as prednisone sometimes are used to relieve severe allergy symptoms. Because the long-term use of corticosteroids can cause serious side effects such as cataracts, osteoporosis and muscle weakness, they’re usually prescribed for only short periods of time.

Other treatments for hay fever include:

Allergy shots (immunotherapy). If medications don’t relieve your hay fever symptoms or cause too many side effects, your doctor may recommend allergy shots (immunotherapy or desensitization therapy). Over three to five years, you’ll receive regular injections containing tiny amounts of allergens. The goal is to get your body used to the allergens that cause your symptoms, and decrease your need for medications.

Immunotherapy might be especially effective if you’re allergic to cat dander, dust mites, or pollen produced by trees, grass or weeds. In children, immunotherapy may help prevent the development of asthma.

Under-the-tongue (sublingual) allergy tablets. Rather than getting shots, you have tiny amounts of allergen in pill form dissolve in your mouth, usually daily.

Rinsing your sinuses. Rinsing your nasal passages with distilled, sterile saline (nasal irrigation) is a quick, inexpensive and effective way to relieve nasal congestion. Rinsing flushes out mucus and allergens from your nose.

Look for a squeeze bottle or a neti pot — a small container with a spout designed for nose rinsing — at your pharmacy or health food store. Use water that’s distilled, sterile, previously boiled and cooled, or filtered using a filter with an absolute pore size of 1 micron or smaller to make up the saline irrigation solution. Also be sure to rinse the irrigation device after each use with similarly distilled, sterile, previously boiled and cooled, or filtered water and leave open to air-dry.

Hay fever home remedies

If you have hay fever, you can help manage the condition in a number of different ways:

  • identify the cause of the allergy and then avoiding further contact with it
  • wash your hands, then bathe your eyes with cold water if they are itchy or sore
  • avoid smoking or breathing in other people’s smoke, as it can make symptoms worse – for advice on quitting smoking, visit Quit smoking
  • avoid going outdoors on days with high pollen counts (particularly before noon), on windy days or after thunderstorms
  • keep windows and doors shut when the pollen count is high
  • keep car windows closed and consider buying a pollen filter for the air vents
  • if your symptoms are triggered by grass, avoid grassy areas and don’t cut grass
  • avoid fresh flowers if that’s the cause of your symptoms
  • when outdoors, wear wrap-around sunglasses to stop pollen getting in your eyes
  • if your hay fever is really bad, wear a face mask when outdoors
  • change clothes and shower after being outdoors to wash off pollen
  • dry bed linen indoors during the pollen season.

There are medicines to ease hay fever symptoms. Some of them are only suitable for adults. You should ask a pharmacist for advice before buying any hay fever medicines for yourself or for a child.

Always follow the manufacturer’s instructions when taking or giving any medicines, and if you are pregnant you should discuss the risks and benefits with a pharmacist before taking any medicines.

Common, over-the-counter hay fever medicines include:

  • antihistamines may ease mild symptoms
  • a steroid nasal spray may ease a blocked or runny nose
  • eye drops may help relieve itchy or watery eyes.

It’s not possible to completely avoid allergens, but you can reduce your symptoms by limiting your exposure to them. If you know what you’re allergic to, you can avoid your triggers.

Pollen or molds

  • Close doors and windows during pollen season.
  • Don’t hang laundry outside — pollen can stick to sheets and towels.
  • Use air conditioning in your house and car.
  • Use an allergy-grade filter in your home ventilation system and change it regularly.
  • Avoid outdoor activity in the early morning, when pollen counts are highest.
  • Stay indoors on dry, windy days.
  • Use a dehumidifier to reduce indoor humidity.
  • Use a high-efficiency particulate air (HEPA) filter in your bedroom and other rooms where you spend a lot of time.
  • Avoid mowing the lawn or raking leaves.
  • Wear a dust mask when cleaning house or gardening.

Dust mites

  • Use allergy-proof covers on mattresses, box springs and pillows.
  • Wash sheets and blankets in water heated to at least 130 F (54 C).
  • Use a dehumidifier or air conditioner to reduce indoor humidity.
  • Vacuum carpets weekly with a vacuum cleaner equipped with a small-particle or HEPA filter.
  • Spray insecticide designed to kill dust mites (acaricides) and approved for indoor use on carpets, furniture and bedding.
  • Consider removing carpeting, especially where you sleep, if you’re highly sensitive to dust mites.

Cockroaches

  • Block cracks and crevices where roaches can enter.
  • Fix leaky faucets and pipes.
  • Wash dishes and empty garbage daily.
  • Sweep food crumbs from counters and floors.
  • Store food, including pet food, in sealed containers.
  • Consider professional pest extermination.

Pet dander

  • Keep pets out of your home, if possible.
  • Bathe dogs twice a week, if possible. The benefit of bathing cats hasn’t been proven.
  • Keep pets out of the bedroom and off furniture.

Alternative medicine

While there isn’t much evidence about how well they work, a number of people try alternative treatments for hay fever. These include:

Herbal remedies and supplements. Extracts of the shrub butterbur may help prevent seasonal allergy symptoms. If you do try butterbur, be sure to use a product that’s labeled “PA-free,” which indicates it’s had potentially toxic substances removed.

There’s some limited evidence that spirulina and Tinospora cordifolia also may be effective. Though their benefits are unclear, other herbal remedies for seasonal allergies include capsicum, honey, vitamin C and fish oil.

Acupuncture. Some people claim acupuncture can help with seasonal allergy symptoms. There’s limited evidence that these treatments work, and there’s little evidence of harm.

Food allergy

A food allergy occurs when the immune system responds to an allergen (an ingredient that is usually harmless) in food. This triggers an immune reaction, which can range from mild to severe. Even a tiny amount of the allergy-causing food can trigger signs and symptoms such as digestive problems, hives or swollen airways. In some people, a food allergy can cause severe symptoms or even a life-threatening reaction known as anaphylaxis.

Food allergy affects an estimated 6 to 8 percent of children under age 3 and up to 3 percent of adults.

The majority of food allergies in children are not severe and while there’s no cure, usually children will outgrow many allergies with time. Some allergies, particularly nut and seafood allergies are less likely to decrease with age.

It’s easy to confuse a food allergy with a much more common reaction known as food intolerance. While bothersome, food intolerance is a less serious condition that does not involve the immune system.

Food allergy symptoms

For some people, an allergic reaction to a particular food may be uncomfortable but not severe. For other people, an allergic food reaction can be frightening and even life-threatening. Food allergy symptoms usually develop within a few minutes to two hours after eating the offending food.

Symptoms of a mild allergy include:

  • hives (red circular weals on the skin)
  • swelling of the face or around the mouth
  • vomiting
  • abdominal discomfort or pain.

Symptoms of severe allergy may include:

  • trouble breathing
  • difficulty talking more than a few words
  • wheeze
  • cough
  • tightness of the throat
  • collapse
  • light-headedness or dizziness
  • diarrhea.

Anaphylaxis

In some people, a food allergy can trigger a severe allergic reaction called anaphylaxis. This can cause life-threatening signs and symptoms, including:

  • Constriction and tightening of the airways
  • A swollen throat or the sensation of a lump in your throat that makes it difficult to breathe
  • Shock with a severe drop in blood pressure
  • Rapid pulse
  • Dizziness, lightheadedness or loss of consciousness

A severe allergic reaction (anaphylaxis) is a medical emergency. Call your local emergency immediately. Lay the person down. If they have an adrenaline injector and you are able to administer it, do so.

Causes of food allergy

When you have a food allergy, your immune system mistakenly identifies a specific food or a substance in food as something harmful. In respose, your immune system triggers cells to release an antibody known as immunoglobulin E (IgE) to neutralize the allergy-causing food or food substance (the allergen).

The next time you eat even the smallest amount of that food, IgE antibodies sense it and signal your immune system to release a chemical called histamine, as well as other chemicals, into your bloodstream. These chemicals cause allergy symptoms.

Some foods are more likely to cause allergies than others. These include:

  • dairy (including milk)
  • peanuts
  • walnuts, almonds, pine nuts, brazil nuts, pecans and other tree nuts
  • soy
  • grains that contain gluten (wheat, barley, rye and oats)
  • fish and shellfish.

In adults, the majority of food allergies are triggered by certain proteins in:

  • Shellfish, such as shrimp, lobster and crab
  • Peanuts
  • Tree nuts, such as walnuts and pecans
  • Fish

In children, food allergies are commonly triggered by proteins in:

  • Peanuts
  • Tree nuts
  • Eggs
  • Cow’s milk
  • Wheat
  • Soy

Pollen-food allergy syndrome

Also known as oral allergy syndrome, pollen-food allergy syndrome affects many people who have hay fever. In this condition, certain fresh fruits and vegetables or nuts and spices can trigger an allergic reaction that causes the mouth to tingle or itch. In serious cases, the reaction results in swelling of the throat or even anaphylaxis.

Proteins in certain fruits, vegetables, nuts and spices cause the reaction because they’re similar to allergy-causing proteins found in certain pollens. This is an example of cross-reactivity.

When you cook foods that trigger pollen-food allergy syndrome, your symptoms may be less severe.

This following table shows the specific fruits, vegetables, nuts and spices that can cause pollen-food allergy syndrome in people who are allergic to different pollens.

If you are allergic to:Birch pollenRagweed pollenGrassesMugwort pollen
You may also have a reaction to:Almond
Apple
Apricot
Carrot
Celery
Cherry
Hazelnut
Peach
Peanut
Pear
Plum
Raw potatoes
Soybean
Some herbs and spices (anise, caraway, coriander, fennel, parsley)
Bananas
Cucumber
Melons (cantaloupe, honeydew and watermelon)
Zucchini
Cucumber
Melons (cantaloupe, honeydew and watermelon)
Orange
Peanut
Tomatoes
White potato
Zucchini
Apples
Bell pepper
Broccoli
Cabbage
Carrots
Celery
Cauliflower
Garlic
Onion
Peach
Some herbs and spices (anise, black pepper, caraway seed, coriander, fennel, mustard, parsley)

Exercise-induced food allergy

Eating certain foods may cause some people to feel itchy and lightheaded soon after starting to exercise. Serious cases may even involve hives or anaphylaxis. Not eating for a couple of hours before exercising and avoiding certain foods may help prevent this problem.

Food intolerance and other reactions

A food intolerance or a reaction to another substance you ate may cause the same signs and symptoms as a food allergy does — such as nausea, vomiting, cramping and diarrhea.

Depending on the type of food intolerance you have, you may be able to eat small amounts of problem foods without a reaction. By contrast, if you have a true food allergy, even a tiny amount of food may trigger an allergic reaction.

One of the tricky aspects of diagnosing food intolerance is that some people are sensitive not to the food itself but to a substance or ingredient used in the preparation of the food.

Common conditions that can cause symptoms mistaken for a food allergy include:

  • Absence of an enzyme needed to fully digest a food. You may not have adequate amounts of some enzymes needed to digest certain foods. Insufficient quantities of the enzyme lactase, for example, reduce your ability to digest lactose, the main sugar in milk products. Lactose intolerance can cause bloating, cramping, diarrhea and excess gas.
  • Food poisoning. Sometimes food poisoning can mimic an allergic reaction. Bacteria in spoiled tuna and other fish also can make a toxin that triggers harmful reactions.
  • Sensitivity to food additives. Some people have digestive reactions and other symptoms after eating certain food additives. For example, sulfites used to preserve dried fruit, canned goods and wine can trigger asthma attacks in sensitive people.
  • Histamine toxicity. Certain fish, such as tuna or mackerel, that are not refrigerated properly and that contain high amounts of bacteria may also contain high levels of histamine that trigger symptoms similar to those of food allergy. Rather than an allergic reaction, this is known as histamine toxicity or scombroid poisoning.
  • Celiac disease. While celiac disease is sometimes referred to as a gluten allergy, it does not result in anaphylaxis. Like a food allergy, it does involve an immune system response, but it’s a unique reaction that’s more complex than a simple food allergy.

This chronic digestive condition is triggered by eating gluten, a protein found in bread, pasta, cookies, and many other foods containing wheat, barley or rye.

If you have celiac disease and eat foods containing gluten, an immune reaction occurs that causes damage to the surface of your small intestine, leading to an inability to absorb certain nutrients.

Risk factors for Food allergy

Food allergy risk factors include:

Family history. You’re at increased risk of food allergies if asthma, eczema, hives or allergies such as hay fever are common in your family.

Other allergies. If you’re already allergic to one food, you may be at increased risk of becoming allergic to another. Similarly, if you have other types of allergic reactions, such as hay fever or eczema, your risk of having a food allergy is greater.

Age. Food allergies are more common in children, especially toddlers and infants. As you grow older, your digestive system matures and your body is less likely to absorb food or food components that trigger allergies.

Fortunately, children typically outgrow allergies to milk, soy, wheat and eggs. Severe allergies and allergies to nuts and shellfish are more likely to be lifelong.

Asthma. Asthma and food allergy commonly occur together. When they do, both food allergy and asthma symptoms are more likely to be severe.

Factors that may increase your risk of developing an anaphylactic reaction include:

  • Having a history of asthma
  • Being a teenager or younger
  • Delaying use of epinephrine to treat your food allergy symptoms
  • Not having hives or other skin symptoms

Complications of food allergy

Complications of food allergy can include:

  • Anaphylaxis. This is a life-threatening allergic reaction.
  • Atopic dermatitis (eczema). Food allergy may cause a skin reaction, such as eczema.

Prevention of food allergy

The best way to prevent an allergic reaction is to know and avoid foods that cause signs and symptoms. For some people, this is a mere inconvenience, but others find it a greater hardship. Also, some foods — when used as ingredients in certain dishes — may be well-hidden. This is especially true in restaurants and in other social settings.

If you know you have a food allergy, follow these steps:

  • Know what you’re eating and drinking. Be sure to read food labels carefully.
  • If you have already had a severe reaction, wear a medical alert bracelet or necklace that lets others know that you have a food allergy in case you have a reaction and you’re unable to communicate.
  • Talk with your doctor about prescribing emergency epinephrine. You may need to carry an epinephrine autoinjector (Adrenaclick, EpiPen) if you’re at risk of a severe allergic reaction.
  • Be careful at restaurants. Be certain your server or chef is aware that you absolutely can’t eat the food you’re allergic to, and you need to be completely certain that the meal you order doesn’t contain it. Also, make sure food isn’t prepared on surfaces or in pans that contained any of the food you’re allergic to. Don’t be reluctant to make your needs known. Restaurant staff members are usually more than happy to help when they clearly understand your request.
  • Plan meals and snacks before leaving home. If necessary, take a cooler packed with allergen-free foods when you travel or go to an event. If you or your child can’t have the cake or dessert at a party, bring an approved special treat so no one feels left out of the celebration.

If your child has a food allergy, take these precautions to ensure his or her safety:

  • Notify key people that your child has a food allergy. Talk with child care providers, school personnel, parents of your child’s friends and other adults who regularly interact with your child. Emphasize that an allergic reaction can be life-threatening and requires immediate action. Make sure that your child also knows to ask for help right away if he or she reacts to food.
  • Explain food allergy symptoms. Teach the adults who spend time with your child how to recognize signs and symptoms of an allergic reaction.
  • Write an action plan. Your plan should describe how to care for your child when he or she has an allergic reaction to food. Provide a copy of the plan to your child’s school nurse and others who care for and supervise your child.
  • Have your child wear a medical alert bracelet or necklace. This alert lists your child’s allergy symptoms and explains how others can provide first aid in an emergency.

Food allergy diagnosis

There’s no perfect test used to confirm or rule out a food allergy. Your doctor will consider a number of factors before making a diagnosis. These factors include.

  • Your symptoms. Give your doctor a detailed history of your symptoms — which foods, and how much, seem to cause problems.
  • Your family history of allergies. Also share information about members of your family who have allergies of any kind.
  • A physical examination. A careful exam can often identify or exclude other medical problems.
  • A skin test. A skin prick test can determine your reaction to a particular food. In this test, a small amount of the suspected food is placed on the skin of your forearm or back. A doctor or another health professional then pricks your skin with a needle to allow a tiny amount of the substance beneath your skin surface. If you’re allergic to a particular substance being tested, you develop a raised bump or reaction. Keep in mind, a positive reaction to this test alone isn’t enough to confirm a food allergy.
  • A blood test. A blood test can measure your immune system’s response to particular foods by measuring the allergy-related antibody known as immunoglobulin E (IgE).For this test, a blood sample taken in your doctor’s office is sent to a medical laboratory, where different foods can be tested.
  • Elimination diet.You may be asked to eliminate suspect foods for a week or two and then add the food items back into your diet one at a time. This process can help link symptoms to specific foods. However, elimination diets aren’t foolproof. An elimination diet can’t tell you whether your reaction to a food is a true allergy instead of a food sensitivity. Also, if you’ve had a severe reaction to a food in the past, an elimination diet may not be safe.
  • Oral food challenge. During this test, done in the doctor’s office, you’ll be given small but increasing amounts of the food suspected of causing your symptoms. If you don’t have a reaction during this test, you may be able to include this food in your diet again.

Treatment for food allergy

The only way to avoid an allergic reaction is to avoid the foods that cause signs and symptoms. However, despite your best efforts, you may come into contact with a food that causes a reaction.

For a minor allergic reaction, over-the-counter or prescribed antihistamines may help reduce symptoms. These drugs can be taken after exposure to an allergy-causing food to help relieve itching or hives. However, antihistamines can’t treat a severe allergic reaction.

For a severe allergic reaction, you may need an emergency injection of epinephrine and a trip to the emergency room. Many people with allergies carry an epinephrine autoinjector (Adrenaclick, EpiPen). This device is a combined syringe and concealed needle that injects a single dose of medication when pressed against your thigh.

If your doctor has prescribed an epinephrine autoinjector:

  • Be sure you know how to use the autoinjector. Also, make sure the people closest to you know how to administer the drug — if they’re with you in an anaphylactic emergency, they could save your life.
  • Carry it with you at all times. It may be a good idea to keep an extra autoinjector in your car or in your desk at work.
  • Always be sure to replace epinephrine before its expiration date or it may not work properly.

Experimental treatments

While there’s ongoing research to find better treatments to reduce food allergy symptoms and prevent allergy attacks, there isn’t any proven treatment that can prevent or completely relieve symptoms.

Treatments being studied are:

Anti-IgE therapy. The medication omalizumab (Xolair) interferes with the body’s ability to use IgE. The drug is currently being studied for treatment of allergic asthma and food allergies.

This treatment is still considered experimental, and more research needs to be done on the drug’s long-term safety. It has been associated with a potential increased risk of anaphylaxis.

Oral immunotherapy. Researchers have been studying the use of oral immunotherapy as a treatment for food allergy. Small doses of the food you’re allergic to are swallowed or placed under your tongue (sublingual). The dose of the allergy-provoking food is gradually increased.

Initial results look promising, even in people with peanut, egg and milk allergies. But more research needs to be done to ensure that this treatment is safe.

Early exposure. In the past, it’s been generally recommended that children avoid allergenic foods to reduce the likelihood of developing allergies. But in a recent study, high-risk infants — such as those with atopic dermatitis or egg allergy or both — were selected to either ingest or avoid peanut products from 4 to 11 months of age until 5 years of age.

Researchers found that high-risk children who regularly consumed peanut protein, such as peanut butter or peanut-flavored snacks, were 70 to 86 percent less likely to develop a peanut allergy. These findings may impact food allergy guidelines in the future.

Food allergy home remedies

One of the keys to preventing an allergic reaction is to completely avoid the food that causes your symptoms.

Don’t assume. Always read food labels to make sure they don’t contain an ingredient you’re allergic to. Even if you think you know what’s in a food, check the label. Ingredients sometimes change.

Food labels are required to clearly list whether they contain any common food allergens. Read food labels carefully to avoid the most common sources of food allergens: milk, eggs, peanuts, tree nuts, fish, shellfish, soy and wheat.

When in doubt, say no thanks. At restaurants and social gatherings, you’re always taking a risk that you might eat a food you’re allergic to. Many people don’t understand the seriousness of an allergic food reaction and may not realize that a tiny amount of a food can cause a severe reaction in some people.

If you have any suspicion at all that a food may contain something you’re allergic to, steer clear.

Involve caregivers. If your child has a food allergy, enlist the help of relatives, baby sitters, teachers and other caregivers. Make sure that they understand how important it is for your child to avoid the allergy-causing food and they know what to do in an emergency.

It’s also important to let caregivers know what steps they can take to prevent a reaction in the first place, such as careful hand-washing and cleaning any surfaces that might have come in contact with the allergy-causing food.

Alternative medicine

Research on alternative food allergy treatments is limited. However, many people do try them and claim that certain treatments help.

Acupuncture point injection therapy has been found to be beneficial for the treatment of hives, although more research is needed to confirm these findings. If you decide to try one of these treatments, be sure you work with an experienced and certified provider.

Allergy diagnosis

Your doctor can offer advice and treatment for mild allergies with a clear cause.

If your allergy is more severe or it’s not obvious what you’re allergic to, you may be referred for allergy testing at a specialist allergy clinic.

Allergy testing

You may benefit from allergy testing if you suffer from asthma or hay fever, or if you have a reaction to insect stings or certain foods.Testing can detect allergies to dust mites, animal dander, mold spores, pollens, certain foods, some insect stings, chemicals and even certain medications.

It is important that allergy tests are carried out and interpreted by trained health professionals. Your doctor may refer you to a specialist immunologist or allergist if a more complicated assessment is needed. It is important that the results of allergy tests are assessed alongside your medical history.

Some alternative practitioners offer allergy tests and treatments. These tests are often expensive and may be of little or no use in correctly detecting allergies.

Types of allergy tests

The most common forms of allergy tests are the skin prick test and the blood test.

If you have skin prick testing, you would be pricked on the arm or back a number of times, with a tiny amount of allergen dropped onto the pinprick. If you are allergic, where you were pricked will become swollen and itchy. This generally subsides within two hours. Although skin prick testing can be uncomfortable, most people find it tolerable. The results are available within 20 minutes.

Blood tests can be also used to test for allergies.

Other, less common allergy tests include:

  • intradermal skin testing
  • patch testing
  • oral allergen testing.

Allergy skin tests

During allergy skin tests, your skin is exposed to suspected allergy-causing substances (allergens) and is then observed for signs of an allergic reaction.

Along with your medical history, allergy tests may be able to confirm whether or not a particular substance you touch, breathe or eat is causing symptoms.

Information from allergy tests may help your doctor develop an allergy treatment plan that includes allergen avoidance, medications or allergy shots (immunotherapy).

Before you leave your doctor’s office, you’ll know the results of a skin prick test or an intradermal test. A patch test may take several days or more to produce results.

A positive skin test means that you may be allergic to a particular substance. Bigger wheals usually indicate a greater degree of sensitivity. A negative skin test means that you probably aren’t allergic to a particular allergen.

Keep in mind, skin tests aren’t always accurate. They sometimes indicate an allergy when there isn’t one (false positive), or skin testing may not trigger a reaction when you’re exposed to something that you are allergic to (false negative). You may react differently to the same test performed on different occasions. Or you may react positively to a substance during a test but not react to it in everyday life.

Your allergy treatment plan may include medications, immunotherapy, changes to your work or home environment, or dietary changes. Ask your doctor to explain anything about your diagnosis or treatment that you don’t understand. With test results that identify your allergens and a treatment plan to help you take control, you’ll be able to reduce or eliminate allergy signs and symptoms.

Allergy skin tests are widely used to help diagnose allergic conditions, including:

  • Hay fever (allergic rhinitis)
  • Allergic asthma
  • Dermatitis (eczema)
  • Food allergies
  • Penicillin allergy
  • Bee venom allergy
  • Latex allergy

Skin tests are generally safe for adults and children of all ages, including infants. In certain circumstances, though, skin tests aren’t recommended.

Your doctor may advise against skin testing if you:

  • Have ever had a severe allergic reaction. You may be so sensitive to certain substances that even the tiny amounts used in skin tests could trigger a life-threatening reaction (anaphylaxis).
  • Take medications that could interfere with test results. These include antihistamines, many antidepressants and some heartburn medications. Your doctor may determine that it’s better for you to continue taking these medications than to temporarily discontinue them in preparation for a skin test.
  • Have certain skin conditions. If severe eczema or psoriasis affects large areas of skin on your arms and back — the usual testing sites — there may not be enough clear, uninvolved skin to do an effective test. Other skin conditions, such as dermatographism, can cause unreliable test results.

Blood tests (in vitro immunoglobulin E antibody tests) can be useful for those who shouldn’t undergo skin tests. Blood tests aren’t done as often as skin tests because they can be less sensitive than skin tests and are more expensive.

In general, allergy skin tests are most reliable for diagnosing allergies to airborne substances, such as pollen, pet dander and dust mites. Skin testing may help diagnose food allergies. But because food allergies can be complex, you may need additional tests or procedures.

Allergy skin test preparation

Before recommending a skin test, your doctor will ask you detailed questions about your medical history, your signs and symptoms, and your usual way of treating them. Your answers can help your doctor determine if allergies run in your family and if an allergic reaction is most likely causing your symptoms. Your doctor may also perform a physical examination to search for additional clues about the cause of your signs and symptoms.

Medications can interfere with allergy skin test results

Before scheduling a skin test, bring your doctor a list of all of your prescription and over-the-counter medications. Some medications can suppress allergic reactions, preventing the skin testing from giving accurate results. Other medications may increase your risk of developing a severe allergic reaction during a test.

Because medications clear out of your system at different rates, your doctor may ask that you stop taking certain medications for up to 10 days.

Medications that can interfere with skin tests include:

  • Prescription antihistamines, such as levocetirizine (Xyzal) and desloratadine (Clarinex).
  • Over-the-counter antihistamines, such as loratadine (Claritin, Alavert), diphenhydramine (Benadryl, others), chlorpheniramine (Chlor-Trimeton), cetirizine (Zyrtec, others) and fexofenadine (Allegra).
  • Tricyclic antidepressants, such as nortriptyline (Pamelor) and desipramine (Norpramin).
  • Certain heartburn medications, such as cimetidine (Tagamet) and ranitidine (Zantac).
  • The asthma medication omalizumab (Xolair). This medication can disrupt test results for six months or longer even after you quit using it (most medications affect results for days to weeks).

How allergy skin test is done

Skin testing is usually done at a doctor’s office. A nurse generally administers the test, and a doctor interprets the results. Typically, this test takes about 20 to 40 minutes. Some tests detect immediate allergic reactions, which develop within minutes of exposure to an allergen. Other tests detect delayed allergic reactions, which develop over a period of several days.

Skin prick test

A skin prick test, also called a puncture or scratch test, checks for immediate allergic reactions to as many as 40 different substances at once. This test is usually done to identify allergies to pollen, mold, pet dander, dust mites and foods. In adults, the test is usually done on the forearm. Children may be tested on the upper back.

Allergy skin tests aren’t painful. This type of testing uses needles (lancets) that barely penetrate the skin’s surface. You won’t bleed or feel more than mild, momentary discomfort.

After cleaning the test site with alcohol, the nurse draws small marks on your skin and applies a drop of allergen extract next to each mark. He or she then uses a lancet to prick the extracts into the skin’s surface. A new lancet is used for each allergen.

To see if your skin is reacting normally, two additional substances are scratched into your skin’s surface:

  • Histamine. In most people, this substance causes a skin response. If you don’t react to histamine, your allergy skin test may not reveal an allergy even if you have one.
  • Glycerin or saline. In most people, these substances don’t cause any reaction. If you do react to glycerin or saline, you may have sensitive skin. Test results will need to be interpreted cautiously to avoid a false allergy diagnosis.

About 15 minutes after the skin pricks, the nurse observes your skin for signs of allergic reactions. If you are allergic to one of the substances tested, you’ll develop a raised, red, itchy bump (wheal) that may look like a mosquito bite. A nurse will then measure the bump’s size.

After the nurse records the results, he or she will clean your skin with alcohol to remove the marks.

Skin injection test

You may need a test that uses a needle to inject a small amount of allergen extract just into the skin on your arm (intradermal test). The injection site is examined after about 15 minutes for signs of an allergic reaction. Your doctor may recommend this test to check for an allergy to insect venom or penicillin.

Patch test

Patch testing is generally done to see whether a particular substance is causing allergic skin irritation (contact dermatitis). Patch tests can detect delayed allergic reactions, which can take several days to develop.

Patch tests don’t use needles. Instead, allergens are applied to patches, which are then placed on your skin. During a patch test, your skin may be exposed to 20 to 30 extracts of substances that can cause contact dermatitis. These can include latex, medications, fragrances, preservatives, hair dyes, metals and resins.

You wear the patches on your arm or back for 48 hours. During this time, you should avoid bathing and activities that cause heavy sweating. The patches are removed when you return to your doctor’s office. Irritated skin at the patch site may indicate an allergy.

Allergy skin test risks

The most common side effect of skin testing is slightly swollen, red, itchy bumps (wheals). These wheals may be most noticeable during the test. In some people, though, an area of swelling, redness and itching may develop a few hours after the test and persist for as long as a couple of days.

Rarely, allergy skin tests can produce a severe, immediate allergic reaction, so it’s important to have skin tests performed at an office where appropriate emergency equipment and medications are available.

Elimination diet

If you have a suspected food allergy, you may be advised to avoid eating a particular food to see if your symptoms improve.

After a few weeks, you may then be asked to eat the food again to check if you have another reaction.

Don’t attempt to do this yourself without discussing it with a qualified healthcare professional.

Challenge testing

In a few cases, a test called a food challenge may also be used to diagnose a food allergy.

During the test, you’re given the food you think you’re allergic to in gradually increasing amounts, to see how you react under close supervision.

This test is riskier than other forms of testing, as it could cause a severe reaction, but is the most accurate way to diagnose food allergies. And challenge testing is always carried out in a clinic where a severe reaction can be treated if it does develop.

Allergy relief and treatment

Allergy shots

Allergy shots are injections you receive at regular intervals over a period of approximately three to five years to stop or reduce allergy attacks. Allergy shots are a form of treatment called immunotherapy. Each allergy shot contains a tiny amount of the specific substance or substances that trigger your allergic reactions. These are called allergens. Allergy shots contain just enough allergens to stimulate your immune system — but not enough to cause a full-blown allergic reaction.

Over time, your doctor increases the dose of allergens in each of your allergy shots. This helps get your body used to the allergens (desensitization). Your immune system builds up a tolerance to the allergens, causing your allergy symptoms to diminish over time.

Your allergy symptoms won’t stop overnight. They usually improve during the first year of treatment, but the most noticeable improvement often happens during the second year. By the third year, most people are desensitized to the allergens contained in the shots — and no longer have significant allergic reactions to those substances.

After a few years of successful treatment, some people don’t have significant allergy problems even after allergy shots are stopped. Other people need ongoing shots to keep symptoms under control.

Allergy shots may be a good treatment choice for you if:

  • Medications don’t control your symptoms well, and you can’t avoid the things that cause your allergic reactions
  • Allergy medications interact with other medications you need to take or cause bothersome side effects
  • You want to reduce your long-term use of allergy medication
  • You’re allergic to insect stings

Allergy shots can be used to control symptoms triggered by:

  • Seasonal allergies. If you have seasonal allergic asthma or hay fever symptoms, you may be allergic to pollens released by trees, grasses or weeds.
  • Indoor allergens. If you have year-round symptoms, you may be sensitive to indoor allergens, such as dust mites, cockroaches, mold, or dander from pets such as cats or dogs.
  • Insect stings. Allergic reactions to insect stings can be triggered by bees, wasps, hornets or yellow jackets.

Allergy shots aren’t available for food allergies or chronic hives (urticaria).

How allergy shots are done

Allergy shots are usually injected in the upper arm.

To be effective, allergy shots are given on a schedule that involves two phases:

  • The buildup phase generally takes three to six months. Typically shots are given one to three times a week. During the buildup phase, the allergen dose is gradually increased with each shot.
  • The maintenance phase generally continues for three to five years or longer. You’ll need maintenance shots about once a month.

In some cases the buildup phase is done more quickly (rush immunotherapy), which requires several injections of increasing doses during each doctor visit. This can decrease the amount of time you need to reach the maintenance phase and get relief from allergy symptoms, but it also increases your risk of having a severe reaction.

You will need to remain in the doctor’s office for 30 minutes after each shot, in case you have a reaction.

Allergy shots Risks

Most people don’t have much trouble with allergy shots. But they contain the substances that cause your allergies — so reactions are possible, and can include:

  • Local reactions, which can involve redness, swelling or irritation at the injection site. These common reactions typically begin within a few hours of the injection and clear up soon after.
  • Systemic reactions, which are less common — but potentially more serious. You may develop sneezing, nasal congestion or hives. More-severe reactions may include throat swelling, wheezing or chest tightness.
  • Anaphylaxis is a rare life-threatening reaction to allergy shots. It can cause low blood pressure and trouble breathing. Anaphylaxis often begins within 30 minutes of the injection, but sometimes starts later than that.

If you get weekly or monthly shots on a regular schedule without missing doses, you’re less likely to have a serious reaction.

Taking an antihistamine medication before getting your allergy shot can reduce the risk of a reaction. Check with your doctor to see if this is recommended for you.

The possibility of a severe reaction is scary — but you won’t be on your own. You’ll be observed in the doctor’s office for 30 minutes after each shot, when the most serious reactions usually occur. If you have a severe reaction after you leave, return to your doctor’s office or go to the nearest emergency room.

Allergy medicine

Several types of medications are used to treat allergy symptoms. Here’s more information.

Get your doctor's advice

Work with your doctor to choose the most effective allergy medications and avoid problems. Even over-the-counter allergy medications have side effects, and some allergy medications can cause problems when combined with other medications.

It’s especially important to talk to your doctor about taking allergy medications in the following circumstances:

  • You’re pregnant or breast-feeding.
  • You have a chronic health condition, such as diabetes, glaucoma, osteoporosis or high blood pressure.
  • You’re taking other medications, including herbal supplements.
  • You’re treating allergies in a child. Children need different doses of medication or different medications from adults.
  • You’re treating allergies in an older adult. Some allergy medications can cause confusion, urinary tract symptoms or other side effects in older adults.
  • You’re already taking an allergy medication that isn’t working. Bring the medication with you in its original bottle or package when you see your doctor.

Keep track of your symptoms, when you use your medications and how much you use. This will help your doctor figure out what works best. You might need to try a few medications to determine which are most effective and have the least bothersome side effects for you.

Allergy medication

Allergy medications are available as pills, liquids, inhalers, nasal sprays, eyedrops, skin creams and shots (injections). Some are available over-the-counter; others are available by prescription only. Here’s a summary of the types of allergy medications and why they’re used.

Antihistamines

Antihistamines block histamine, a symptom-causing chemical released by your immune system during an allergic reaction. This reduces the severity of the reaction and eases the symptoms of allergy.

Antihistamines are commonly used in the treatment of a number of conditions related to allergies and hypersensitivities like:

  • hay fever (allergic rhinitis)
  • hives (urticaria)
  • allergic conjunctivitis
  • eczema (contact dermatitis)
  • asthma
  • reactions to bites and stings.

Some antihistamines can also be used to treat non-allergy-related conditions, such as motion sickness, insomnia and heartburn or indigestion.

Oral antihistamines can be used to treat all of the symptoms of an allergic reaction. Others come as eye drops or nasal sprays, for treating specific symptoms only. Some oral antihistamines may have a sedative effect, but others are non-sedating or non-drowsy.

Antihistamines don’t treat very severe allergic reactions like anaphylaxis, as they work too slowly.

Side effects of antihistamines

Some people get side effects from oral antihistamines like:

  • tiredness
  • drowsiness
  • headache
  • dry mouth
  • upset stomach.

They usually don’t last long.

If you use antihistamines you should be careful when operating machinery, such as driving a car. Even non-sedating antihistamines can make some people drowsy.

You should talk to a pharmacist or doctor before taking an antihistamine if you:

  • have kidney or liver disease
  • are a woman who is pregnant or breastfeeding
  • are a man with prostate enlargement.

People with porphyria should talk to their doctor or pharmacist before taking antihistamines.

If you have any questions or concerns about antihistamines, please talk to your doctor or pharmacist.

Pills and liquids

Oral antihistamines, available over-the-counter and by prescription, ease a runny nose, itchy or watery eyes, hives, swelling, and other signs or symptoms of allergies. Because some of these drugs can cause drowsiness and fatigue, take them with caution when you need to drive or do other activities that require alertness.

Antihistamines that tend to cause drowsiness include:

  • Diphenhydramine
  • Chlorpheniramine

These antihistamines are much less likely to cause drowsiness:

  • Cetirizine (Zyrtec Allergy)
  • Desloratadine (Clarinex)
  • Fexofenadine (Allegra Allergy)
  • Levocetirizine (Xyzal)
  • Loratadine (Alavert, Claritin)

Nasal sprays

Antihistamine nasal sprays help relieve sneezing, itchy or runny nose, sinus congestion, and postnasal drip. Side effects of antihistamine nasal sprays might include a bitter taste, drowsiness or fatigue. Prescription antihistamine nasal sprays include:

  • Azelastine (Astelin, Astepro)
  • Olopatadine (Patanase)

Eyedrops

Antihistamine eyedrops, available over-the-counter or by prescription, can ease itchy, red, swollen eyes. These drops might have a combination of antihistamines and other medicines.

Side effects might include headache and dry eyes. If antihistamine drops sting or burn, try keeping them in the refrigerator or using refrigerated artificial-tear drops before you use the medicated drops. Examples include:

  • Azelastine (Optivar)
  • Emedastine (Emadine)
  • Ketotifen (Alaway)
  • Olopatadine (Pataday, Patanol, Pazeo)
  • Pheniramine (Visine-A, Opcon-A, others)

Decongestants

Decongestants are used for quick, temporary relief of nasal and sinus congestion. They can cause insomnia, headache, increased blood pressure and irritability. They’re not recommended for pregnant women or for people with high blood pressure, cardiovascular disease, glaucoma or hyperthyroidism.

Pills and liquids

Oral decongestants relieve nasal and sinus congestion caused by hay fever (allergic rhinitis). Many decongestants, such as pseudoephedrine (Afrinol, Sudafed, others), are available over-the-counter.

A number of oral allergy medications contain a decongestant and an antihistamine. Examples include:

  • Cetirizine and pseudoephedrine (Zyrtec-D)
  • Desloratadine and pseudoephedrine (Clarinex-D)
  • Fexofenadine and pseudoephedrine (Allegra-D)
  • Loratadine and pseudoephedrine (Claritin-D)

Nasal sprays and drops

Nasal decongestant sprays and drops relieve nasal and sinus congestion if used only for a short time. Repeated use of these drugs for more than three consecutive days can result in a cycle of recurring or worsening congestion. Examples include:

  • Oxymetazoline (Afrin, Dristan, others)
  • Tetrahydrozoline (Tyzine)

Corticosteroids

Corticosteroids relieve symptoms by suppressing allergy-related inflammation.

Nasal sprays

Corticosteroid sprays prevent and relieve stuffiness, sneezing and runny nose. Side effects can include an unpleasant smell or taste, nasal irritation, and nosebleeds. Examples include:

  • Budesonide (Rhinocort)
  • Fluticasone furoate (Flonase Sensimist, Veramyst)
  • Fluticasone propionate (Flonase Allergy Relief)
  • Mometasone (Nasonex)
  • Triamcinolone (Nasacort Allergy 24 Hour)

For people who are bothered by the feeling of liquid running down their throats or the taste of the above, there are two aerosol formulas:

  • Beclomethasone (Qnasl)
  • Ciclesonide (Zetonna)

Inhalers

Inhaled corticosteroids are often used daily as part of treatment for asthma caused or complicated by reactions to airborne allergy triggers (allergens). Side effects are generally minor and can include mouth and throat irritation and oral yeast infections.

Some inhalers combine corticosteroids with other asthma medications. Prescription inhalers include:

  • Beclomethasone (Qvar)
  • Budesonide (Pulmicort Flexhaler)
  • Ciclesonide (Alvesco, Zetonna)
  • Fluticasone (Advair Diskus, Flovent Diskus, others)
  • Mometasone (Asmanex Twisthaler)

Eyedrops

Corticosteroid eyedrops are used to relieve persistent itchy, red or watery eyes when other interventions aren’t effective. A physician specializing in eye disorders (ophthalmologist) usually monitors the use of these drops because of the risk of vision impairment, cataracts, glaucoma and infection. Examples include:

  • Fluorometholone (Flarex, FML)
  • Loteprednol (Alrex, Lotemax)
  • Prednisolone (Omnipred, Pred Forte, others)

Pills and liquids

Oral corticosteroids are used to treat severe symptoms caused by all types of allergic reactions. Long-term use can cause cataracts, osteoporosis, muscle weakness, stomach ulcers, increased blood sugar (glucose) and delayed growth in children. Oral corticosteroids can also worsen hypertension.

Prescription oral corticosteroids include:

  • Prednisolone (Prelone)
  • Prednisone (Prednisone Intensol, Rayos)
  • Methylprednisolone (Medrol)

Skin creams

Corticosteroid creams relieve allergic skin reactions such as itching, redness, scaling or other irritations. Some low-potency corticosteroid creams are available without a prescription, but talk to your doctor before using these drugs for more than a few weeks.

Side effects can include skin discoloration and irritation. Long-term use, especially of stronger prescription corticosteroids, can cause thinning of the skin and disruption of normal hormone levels. Examples include:

  • Betamethasone (Dermabet, Diprolene, others)
  • Desonide (Desonate, DesOwen)
  • Hydrocortisone (Cortaid, Micort-HC, others)
  • Mometasone (Elocon)

Mast cell stabilizers

Mast cell stabilizers block the release of immune system chemicals that contribute to allergic reactions. These drugs are generally safe but usually need to be used for several days to reach full effect. They’re usually used when antihistamines are not working or not well-tolerated.

Nasal spray

Generic over-the-counter nasal sprays are sold as cromolyn.

Eyedrops

Prescription eyedrops include the following:

  • Cromolyn (Crolom)
  • Lodoxamide (Alomide)
  • Pemirolast (Alamast)
  • Nedocromil (Alocril)

Leukotriene inhibitors

A leukotriene inhibitor is a prescription medication that blocks symptom-causing chemicals called leukotrienes. This oral medication relieves allergy signs and symptoms including nasal congestion, runny nose and sneezing. Only one type of this drug, montelukast (Singulair), is approved for treating hay fever.

In some people, leukotriene inhibitors can cause psychological symptoms such as irritability, anxiousness, insomnia, hallucinations, aggression, depression, and suicidal thinking or behavior.

Allergen immunotherapy

Immunotherapy is carefully timed and gradually increased exposure to allergens, particularly those that are difficult to avoid, such as pollens, dust mites and molds. The goal is to train your body’s immune system not to react to these allergens.

Immunotherapy might be used when other treatments aren’t effective or tolerated. It might help prevent the development of asthma in some people.

Allergy Shots

Immunotherapy may be administered as a series of injections, usually one or two times a week for three to six months. This is followed by a series of less frequent maintenance shots that usually continue for three to five years.

Side effects might include irritation at the injection site and allergy symptoms such as sneezing, congestion or hives. Rarely, allergy shots can cause anaphylaxis, a sudden life-threatening reaction that causes swelling in the throat, difficulty breathing, and other signs and symptoms.

Sublingual immunotherapy

With this type of immunotherapy, you place an allergen-based tablet under your tongue (sublingual) and allow it to be absorbed. This daily treatment has been shown to reduce runny nose, congestion, eye irritation and other symptoms associated with hay fever. It also improves asthma symptoms and may prevent the development of asthma.

Sublingual immunotherapy tablets contain extracts from pollens of different types of grass, including the following:

  • Short ragweed (Ragwitek)
  • Sweet vernal, orchard, perennial rye, Timothy and Kentucky blue grass (Oralair)
  • Timothy grass (Grastek)

Emergency epinephrine shots

Epinephrine shots are used to treat anaphylaxis, a sudden, life-threatening reaction. The drug is administered with a self-injecting syringe and needle device (autoinjector). You might need to carry two autoinjectors and wear an alert bracelet if you’re likely to have a severe allergic reaction to a certain food, such as peanuts, or if you’re allergic to bee or wasp venom.

A second injection is often needed. Therefore, it’s important to call your local emergency number or get immediate emergency medical care.

Your health care provider will train you on how to use an epinephrine autoinjector. It is important to get the type that your doctor prescribed, as the method for injection may differ slightly for each brand. Also, be sure to replace your emergency epinephrine before the expiration date.

Examples of these medications include:

  • Adrenaclick
  • Auvi-Q
  • EpiPen
  • EpiPen Jr.
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