What is allergic contact dermatitis

Allergic contact dermatitis is a form of dermatitis or eczema caused by an allergic reaction to a material, called an allergen, in contact with your skin. The allergen is harmless to people that are not allergic to it. Allergic contact dermatitis is also called contact allergy. The rash isn’t contagious or life-threatening, but it can be very uncomfortable. Allergic contact dermatitis occurs when a substance to which you’re sensitive (allergen) triggers an immune reaction in your skin. It usually affects only the area that came into contact with the allergen. But it may be triggered by something that enters your body through foods, flavorings, medicine, or medical or dental procedures (systemic contact dermatitis).

Many substances can cause such reactions, including soaps, cosmetics, fragrances, jewelry and plants. You may become sensitized to a strong allergen such as poison ivy after a single exposure. Weaker allergens may require multiple exposures over several years to trigger an allergy. Once you develop an allergy to a substance, even a small amount of it can cause a reaction.

Acute allergic contact dermatitis may look red and swollen with small fluid filled bumps (vesicles). Symptoms occur within a few hours of exposure. With chronic exposure the rash appears like “eczema” and the skin may thicken, scale or crack from scratching. The location of the rash depends on the allergen exposure. For instance, the rash associated with nickel allergy is located in areas of contact (underneath the belly button, ear lobes from earrings, around the neck from necklace). The rash from cosmetics is located on the face and particularly the eyelids. Patients with allergies to rubber gloves will present with hand dermatitis. Your dermatologist can help differentiate allergic contact dermatitis from other types of dermatitis including atopic dermatitis, psoriasis, seborrheic dermatitis and pityriasis rosea.

To treat allergic contact dermatitis successfully, you need to identify and avoid the cause of your reaction. If you can avoid the offending substance, the rash usually clears up in two to four weeks. You can try soothing your skin with cool, wet compresses, anti-itch creams and other self-care steps.

• For acute symptoms, cold compresses can help with the itch.
• For patients with oozing lesions, Burrow’s solution (aluminum triacetate), calamine, and/or oatmeal baths can also be utilized.
• In hand dermatitis, avoiding excessive hand washing and using non-irritating moisturizers is recommended. Choose mild soaps, moisturizers, and detergents without dyes or perfumes. Wear gloves to protect your hands and other body parts from exposure if contact with these chemicals is unavoidable, however be aware that you can become allergic to chemicals in the gloves as well.
• In foot dermatitis, the use of barrier socks may be helpful.
• Wash skin immediately after contact with an allergen to limit the spread and severity of the reaction such as after known contact with a plant allergen (poison ivy).
• Apply covers over metal fasteners in clothing to avoid contact with nickel.

Common allergens include:

• Nickel, which is used in jewelry, buckles and many other items
• Medications, such as antibiotic creams and oral antihistamines
• Balsam of Peru, which is used in many products, such as perfumes, cosmetics, mouth rinses and flavorings
• Formaldehyde, which is in preservatives, disinfectants and clothing
• Personal care products, such as deodorants, body washes, hair dyes, cosmetics and nail polish
• Plants such as poison ivy and mango, which contain a highly allergenic substance called urushiol
• Airborne substances, such as ragweed pollen and spray insecticides
• Products that cause a reaction when you’re in the sun (photoallergic contact dermatitis), such as some sunscreens and oral medications

Children develop the condition from the usual offenders and also from exposure to diapers, baby wipes, sunscreens, clothing with snaps or dyes, and so on.

Allergic contact dermatitis is common in the general population and in specific employment groups.

• Allergic contact dermatitis is more common in women than men, mainly due to nickel allergy and, recently, to acrylate allergy associated with nail cosmetics.
• Many young children are also allergic to nickel (nickel allergy). Nickel is one of the most common causes of allergic contact dermatitis: a skin rash or irritation caused by touching an allergen. In fact, it is estimated that more than 18 percent of people in North America are allergic to nickel, including 11 million children in the U.S. If you have a nickel allergy, the best way to avoid symptoms is to avoid objects containing nickel. However, this can be challenging, since nickel is present in many common household items.
• Contact allergy to topical antibiotics is common in patients over the age of 70 years old.
• Allergic contact dermatitis is especially common in metal workers, hairdressers, beauticians, health care workers, cleaners, painters and florists

Systemic contact dermatitis

Cutaneous sensitization, as in cases of allergic contact dermatitis, has been associated with systemic contact dermatitis ¹. In the latter condition, systemic exposure to a chemical (i.e., oral, inhalant or intravenous) in a patient who has been previously cutaneously sensitized results in a widespread symmetric dermatitis or recall dermatitis localized to the area of previous sensitization ². Ingestion of a contact allergen may rarely may lead to baboon syndrome or generalized systemic contact dermatitis.

Photoallergy

Sometimes contact allergy arises only after the skin has been exposed to ultraviolet light. The rash is confined to sun exposed areas even though the allergen may have been in contact with covered areas. This is called photocontact dermatitis.

Examples of photoallergy include:

• Dermatitis due to a sunscreen chemical, affecting the top but not the under surface of the arm
• Dermatitis of face, neck, arms and hands due to antibacterial soap.

How to treat allergic contact dermatitis

To help reduce itching and soothe inflamed skin, try these self-care approaches:

• Avoid the irritant or allergen. The key to this is identifying what’s causing your rash and staying away from it. Your doctor may give you a list of products that typically contain the substance that affects you. Also ask for a list of products that are free of the substance that affects you. If you’re allergic to the metal in a piece of jewelry, you may be able to wear it by putting a barrier between you and the metal. For example, line the inside of a bracelet with a piece of clear tape or paint it with clear nail polish.
• Apply an anti-itch cream or lotion to the affected area. A nonprescription cream containing at least 1 percent hydrocortisone can temporarily relieve your itch. A steroid ointment may be applied one or two times a day for two to four weeks. Or try calamine lotion.
• Take an oral anti-itch drug. A nonprescription oral corticosteroid or antihistamine, such as diphenhydramine (Benadryl), may be helpful if your itching is severe.
• Apply cool, wet compresses. Moisten soft washcloths and hold them against the rash to soothe your skin for 15 to 30 minutes. Repeat several times a day.
• Avoid scratching. Trim your nails. If you can’t keep from scratching an itchy area, cover it with a dressing.
• Soak in a comfortably cool bath. Sprinkle the water with baking soda or an oatmeal-based bath product.
• Protect your hands. Rinse and dry hands well and gently after washing. Use moisturizers throughout the day. And choose gloves based on what you’re protecting your hands from. For example, plastic gloves lined with cotton are good if your hands are often wet.

Allergic contact dermatitis how long does it last?

Contact allergy often persists lifelong so it is essential to identify the allergen and avoid touching it. Dermatitis may recur on re-exposure to the allergen. Allergic contact dermatitis should be suspected when a rash corresponds to the location of contact with a potentially sensitizing substance. It is important to recognize how you are in contact with the responsible substance so that, where possible, you can avoid it. If you can avoid the offending substance, the rash usually clears up in two to four weeks. You can try soothing your skin with cool, wet compresses, anti-itch creams and other self-care steps.

Allergic contact dermatitis is a delayed hypersensitivity reaction and occurs 48–72 hours after exposure to the allergen. Only a small number of people react to the specific allergen, which is harmless to those who are not allergic to it. Patients with atopic dermatitis associated with defective filaggrin (a structural protein in the stratum corneum) have a high risk of also developing allergic contact dermatitis.

Some typical examples of allergic contact dermatitis include:

• Eczema in skin in contact with jewellery items, due to contact allergy to nickel
• Reactions to fragrances in perfumes and household items
• Eczema under adhesive plaster, due to contact allergy to rosin
• Swelling and blistering of face and neck in reaction to permanent hair dye, due to allergy to paraphenylene diamine
• Hand dermatitis caused by rubber accelerator chemicals used in the manufacture of rubber gloves
• Itchy red face due to contact with methylisothiazolinone, a preservative in wash-off hair products and baby wipes
• Fingertip dermatitis due to acrylates used in hair extensions and nail cosmetics.
• Reactions after dental implants containing acrylates
• Localized blistering at the site of topical medications such as antibiotics
• Swelling and blistering on exposed sites (e.g., face and hands) due to contact with plants such as poison ivy, sumac, oak or the Japanese wax tree Toxicodendron succedanium

There is a very long list of materials that have caused contact allergy in a small number of individuals.

To avoid exposure and reduce symptoms of allergic contact dermatitis, dermatologists recommend the following tips:

1. Choose jewelry carefully. It’s common for a nickel allergy to develop from wearing jewelry containing nickel. Earrings, earring backs and watches are some of the biggest culprits; however necklaces, rings and bracelets containing nickel can also trigger symptoms. To avoid exposure, only wear jewelry that is nickel-free, hypoallergenic, or made from metals such as surgical-grade stainless steel, 18-, 22-, or 24-karat yellow gold, pure sterling silver, or platinum. In addition, wear watchbands made of leather, cloth or plastic.
2. Check your clothing. It’s also common for belt buckles, bra hooks, and metal buttons, zippers and snaps to contain nickel. If your clothing has these, replace them with ones that are plastic or plastic-coated. You can also create a barrier between these items and your skin by coating the items with clear nail polish. However, the nail polish will need to be re-applied often.
3. Cover electronics. Recent reports suggest that some electronic devices, including cell phones, laptops, and tablets, may contain nickel. To avoid exposure, always use a protective cover on your electronic devices.
4. Substitute household objects containing nickel with objects made of other materials. Examples include brass keys, titanium-coated or stainless steel razors, pots and pans with silicone handles, and titanium or plastic eyeglass frames.
5. Avoid foods containing nickel if you are extremely sensitive to nickel. Some foods that contain high amounts of nickel include soy products—such as soybeans, soy sauce, and tofu—licorice, buckwheat, cocoa powder, clams, cashews, and figs.

Rashes caused by a nickel allergy are not life-threatening, but they can be uncomfortable. If you think you have an allergy, or if you have a rash that blisters, becomes infected, or comes and goes, see a board-certified dermatologist for the proper diagnosis.

What causes allergic contact dermatitis?

Allergic contact dermatitis is caused by a substance you’re exposed to that irritates your skin or triggers an allergic reaction. The substance could be one of thousands of known allergens and irritants. Some of these substances may cause both irritant contact dermatitis and allergic contact dermatitis.

Allergic contact dermatitis is a type 4 or delayed hypersensitivity reaction and occurs 48–72 hours after exposure to the allergen. The mechanism involves CD4+ T-lymphocytes, which recognize an antigen on the skin surface, releasing cytokines that activate the immune system and cause the dermatitis. Note:

• Contact allergy occurs predominantly from an allergen on the skin rather than from internal sources or food.
• Only a small number of people react to the specific allergen, which is harmless to those who are not allergic to it.
• They may have been in contact with the allergen for years without it causing dermatitis.
• Contact with tiny quantities of an allergen can induce dermatitis.
• Patients with impaired barrier function of the skin are more prone to allergic contact dermatitis, e.g., patients with leg ulcers, perianal dermatitis, or chronic irritant contact dermatitis.
• Patients with atopic dermatitis associated with defective filaggrin (a structural protein in the stratum corneum) have a high risk of also developing allergic contact dermatitis.

Risk factors for allergic contact dermatitis

Some jobs and hobbies put you at higher risk of contact dermatitis. Examples include:

• Health care and dental employees
• Metalworkers
• Construction workers
• Hairdressers and cosmetologists
• Auto mechanics
• Scuba divers or swimmers, due to the rubber in face masks or goggles
• Cleaners
• Gardeners and agricultural workers
• Cooks and others who work with food

Allergic contact dermatitis prevention

General prevention steps include the following:

• Avoid irritants and allergens. Try to identify and avoid substances that irritate your skin or cause an allergic reaction.
• Wash your skin. You might be able to remove most of the rash-causing substance if you wash your skin right away after coming into contact with it. Use a mild, fragrance-free soap and warm water. Rinse completely. Also wash any clothing or other items that may have come into contact with a plant allergen, such as poison ivy.
• Wear protective clothing or gloves. Face masks, goggles, gloves and other protective items can shield you from irritating substances, including household cleansers.
• Apply an iron-on patch to cover metal fasteners next to your skin. This can help you avoid a reaction to jean snaps, for example.
• Apply a barrier cream or gel. These products can provide a protective layer for your skin. For example, an over-the-counter skin cream containing bentoquatam (IvyBlock) may prevent or lessen your skin’s reaction to poison ivy.
• Use moisturizer. Regularly applying moisturizing lotions can help restore your skin’s outermost layer and keep your skin supple.
• Take care around pets. Allergens from plants, such as poison ivy, can cling to pets and then be spread to people.

Irritant vs Allergic contact dermatitis

Irritant contact dermatitis is due to irritation or repetitive injury to the skin. Irritant contact dermatitis is nonallergic skin reaction occurs when a substance damages your skin’s outer protective layer. Irritants include water, soaps, detergents, solvents, acids, alkalis, urine, stools, saliva and friction. Irritant contact dermatitis may affect anyone, providing they have had enough exposure to the irritant, but those with atopic dermatitis are particularly sensitive. Most cases of hand dermatitis are due to contact with irritants. Irritant contact dermatitis can occur immediately after a single injury or develop slowly after repeated exposure to an irritant. Irritant contact dermatitis is more common than allergic contact dermatitis by a factor of 4:1 in people with contact dermatitis. Irritant contact dermatitis can occur in anyone, especially after repeated exposure. Symptoms are a burning or stinging sensation with redness, swelling or peeling.

Some people react to strong irritants after a single exposure. Others may develop signs and symptoms after repeated exposures to even mild irritants. And some people develop a tolerance to the substance over time.

Common irritants include:

• Solvents
• Rubbing alcohol
• Bleach and detergents
• Shampoos, permanent wave solutions
• Airborne substances, such as sawdust or wool dust
• Plants
• Fertilizers and pesticides

Allergic contact dermatitis symptoms

Allergic contact dermatitis arises some hours after contact with the responsible material. It settles down over some days providing the skin is no longer in contact with the allergen.

Allergic contact dermatitis usually occurs on areas of your body that have been directly exposed to the reaction-causing substance — for example, along a calf that brushed against poison ivy or under a watchband in nickel allergy. The rash usually develops within minutes to hours of exposure and can last two to four weeks.

Signs and symptoms of contact dermatitis include:

• A red rash
• Itching, which may be severe
• Dry, cracked, scaly skin
• Bumps and blisters, sometimes with oozing and crusting
• Swelling, burning or tenderness

Allergic contact dermatitis is generally confined to the site of contact with the allergen, but it may extend outside the contact area or become generalized.

• Transmission from the fingers can lead to dermatitis on the eyelids and genitals.
• Dermatitis is unlikely to be due to a specific allergen if the area of skin most in contact with that allergen is unaffected.
• The affected skin may be red and itchy, swollen and blistered, or dry and bumpy.

Figure 1. Allergic contact dermatitis face

[Source ³ ]

Figure 2. Allergic contact dermatitis

Footnote: A 40-year-old man presented with a severe rash on his left forearm. One week earlier, he had experienced tendonitis in his left elbow and had treated it with diclofenac cream, a topical nonsteroidal anti-inflammatory drug (NSAID), applied four times daily. The area had become slightly erythematous three days later and then rapidly developed blistering on the fourth and fifth days. The eruption was intensely itchy and spread from the elbow to the wrist. Although the patient had noted some improvement in the tendonitis, he stopped using the diclofenac cream on the fifth day because of the rash. He was instructed to stop using diclofenac cream and given oral clarithromycin 250 mg twice daily for five days and fluocinonide 0.05% cream topically twice daily. Although the patient noted an improvement in the rash with use of the fluocinonide 0.05% cream, the dermatitis worsened after one week. The fluocinonide 0.05% cream was discontinued and a course of oral prednisone 40 mg daily was prescribed. The dosage of prednisone was tapered over three weeks, resulting in improvement in the dermatitis. A patch test was performed using the standard screening series of 65 allergens developed by the North American Contact Dermatitis Group, as well as the patient’s own diclofenac cream, fluocinonide 0.05% cream and selected additional allergens. Diluted allergens in Finn chambers were placed on uninvolved skin on the patient’s back and held in place using nonallergenic tape. The patient was instructed to avoid activity that could disturb the chambers, such as bathing or exercise. The Finn chambers and tape were removed at 48 hours, and a reading was performed at 96 hours. Positive skin reactions to propylene glycol (3+) and to the patient’s own diclofenac cream (3+) were found. Positive results were found for other agents in the patch test as well but were not relevant to the dermatitis. Patch-testing on patient showed that the offending agent was not the topical nonsteroidal anti-inflammatory drug (NSAID), but rather propylene glycol, which is present in the vehicle of the cream. Fluocinonide 0.05% cream also contains propylene glycol, hence the worsening of the patient’s dermatitis.

[Source ¹ ]

Allergic contact dermatitis complications

Allergic contact dermatitis starts as a localized reaction to an allergen in contact with the skin, but severe reactions may generalize due to auto-eczematisation, and can lead to erythroderma.

Allergic contact dermatitis can also lead to an infection if you repeatedly scratch the affected area, causing it to become wet and oozing. This creates a good place for bacteria or fungi to grow and may cause an infection.

Allergic contact dermatitis diagnosis

Sometimes it is easy to recognize contact allergy and no specific tests are necessary. Your doctor may be able to diagnose contact dermatitis and identify its cause by talking to you about your signs and symptoms, questioning you to uncover clues about the trigger substance, and examining your skin to note the pattern and intensity of your rash.

• Taking a very good history including information on work environment, hobbies, products in use at home and work and sun exposure will enhance the chances of finding a diagnosis. The rash usually (but not always) completely clears up if the allergen is no longer in contact with the skin, but recurs even with slight contact with it again.

Your doctor may recommend a patch test to see if you’re allergic to something. This test can be useful if the cause of your rash isn’t apparent or if your rash recurs often.

• The open application test is used to confirm contact allergy to a cosmetic, such as a moisturizer. The product under suspicion is applied several times daily for several days to a small area of sensitive skin. The inner aspect of the upper arm is suitable. Contact allergy is likely if dermatitis arises in the treated area.
• Dermatologists will perform patch tests in patients with suspected contact allergy, particularly if the reaction is severe, recurrent or chronic. The tests can identify the specific allergen causing the rash. During a patch test, small amounts of potential allergens are applied to adhesive patches, which are then placed on your skin. The patches remain on your skin for two to three days, during which time you’ll need to keep your back dry. Your doctor then checks for skin reactions under the patches and determines whether further testing is needed.

Fungal scrapings of skin for microscopy and culture can exclude a fungal infection.

Dimethylgloxime test is available to ‘spot test’ if a product contains nickel.

Allergic contact dermatitis treatment

It is important to recognize how you are in contact with the responsible substance so that, where possible, you can avoid it.

• Find out precisely what you are allergic to by having comprehensive patch tests.
• Identify where the allergen is found, thus read labels of all products before use.
• Carefully study your environment to locate the allergen. Note: many chemicals have several names, and cross-reactions to similar chemicals with different names are common.
• Wear appropriate gloves to protect hands from touching materials to which you react and remove gloves in the appropriate way. Some chemicals will penetrate certain gloves; seek a safety expert’s advice.
• Ask your dermatologist to help.

If home care steps don’t ease your signs and symptoms, your doctor may prescribe medications.

Active dermatitis is usually treated with the following:

• Emollient creams
• Steroid creams or ointments. These topically applied creams or ointments help soothe the rash of contact dermatitis. A topical steroid may be applied one or two times a day for two to four weeks.
• Topical or oral antibiotics for secondary infection
• Oral steroids, usually short courses, for severe cases. In severe cases, your doctor may prescribe oral corticosteroids to reduce inflammation, antihistamines to relieve itching or antibiotics to fight a bacterial infection.
• Phototherapy or photochemotherapy.
• Azathioprine, ciclosporin or other immunosuppressive agent.
• Tacrolimus ointment and pimecrolimus cream are immune modulating drugs that inhibit calcineurin and may prove helpful for allergic contact dermatitis.

Topical Steroids

Topical steroids are anti-inflammatory medications. They help to get the rash under control more quickly and are usually applied 1-2 times a day. Topical steroids come in different formulations and strengths. Milder topical steroids such as hydrocortisone can be purchased over the counter. If the rash is not improving after 7 days or getting worse, you should consult your physician. A more potent topical steroid may be required, but should be used sparingly in sensitive areas such as the face, underarms and groin as they can thin the skin and cause stretch marks.

Antihistamines

Antihistamines may be given for the relief of the itch associated with allergic contact dermatitis but topical steroids are likely to be more effective in rash resolution. Sedating oral antihistamines promote sleep but may have side-effects including dryness, difficulty urinating, dizziness and impaired coordination. Sedating antihistamines should be used cautiously in elderly patients for all the above reasons and due to a potential association with dementia. These medications should be used in conjunction with consultation with your doctor / dermatologist.

Topical Immunomodulators

Topical calcineurin inhibitors (pimecrolimus, tacrolimus) are anti-inflammatory agents that may provide another option in patients with allergic contact dermatitis or irritant contact dermatitis. However, they are not FDA approved for allergic contact dermatitis. They do not cause skin thinning, which is beneficial for the treatment of patients with facial dermatitis and dermatitis in other sensitive areas (bending areas, genitals). The most common adverse effects encountered are burning and itch at the application site.

Topical Antibiotics

These creams or ointments are sometimes used if there are open fissures and evidence of a secondary bacterial infection. However over-the-counter topical antibiotics are frequent causes of allergic contact dermatitis and should be used under the recommendation of your allergist / immunologist.

Systemic Steroids

These medications can be given by mouth or injection and may be needed if the rash is severe, associated with swelling, or if the rash covers much of your body. They will lead to rapid improvement and are usually considered safe when prescribed for short periods of time. However, systemic steroids can have significant side effects requiring close monitoring by your physician and are not recommended for long term therapy of allergic contact dermatitis. Some of these side effects can include weight gain, bone thinning, cataracts, glaucoma, easy bruising and sleep disturbances. It is also important to take these medications exactly as directed to avoid a flare in your dermatitis with rapid discontinuation as well as other side effects. Other oral medications that can be tried in difficult to treat cases include cyclosporine, methotrexate, azathioprine, and mycophenolate mofetil.

Phototherapy

Your doctor may refer you to a dermatologist for light therapy if the rash is not responding to the above therapy.

Allergic contact dermatitis prognosis

Contact allergy often persists lifelong so it is essential to identify the allergen and avoid touching it. Dermatitis may recur on re-exposure to the allergen.

• Some allergens are more difficult to avoid than others, with airborne allergens being a particular problem (e.g., epoxy resin, compositae pollen).
• The longer a person suffers from severe allergic contact dermatitis, the longer it will take to clear after the diagnosis is made and the cause detected.
• The dermatitis may clear up on avoidance of contact with the allergen, but sometimes it persists indefinitely, e.g., chromate allergy.

Prognosis depends on patient education and compliance in avoiding allergens and appropriate skin care.

1. Allergic contact dermatitis caused by diclofenac cream. Carrie B. Lynde, Tadeusz A. Pierscianowski, Melanie D. Pratt. CMAJ Dec 2009, 181 (12) 925-926; DOI: 10.1503/cmaj.081784 http://www.cmaj.ca/content/181/12/925[↩][↩]
2. Jacob SE, Zapolanski T. Systemic contact dermatitis. Dermatitis 2008;19:9–15[↩]
3. Bangsgaard, Nannie et al. “Sensitization to and allergic contact dermatitis caused by Mirvaso(®) (brimonidine tartrate) for treatment of rosacea – 2 cases.” Contact dermatitis 74 6 (2016): 378-9[↩]