What is cellulitis

Cellulitis is a common, potentially serious bacterial infection of the skin (the lower dermis) and subcutaneous tissues (just under the skin). The affected skin appears swollen and red and is typically painful and warm to the touch. Cellulitis is usually caused by a bacterial infection and can become serious if not treated with antibiotics. The most common bacteria are Staphylococcus aureus (golden Staph) and group A beta-hemolytic Streptococcus (Streptococcus pyogenes). These bacteria enter broken or normal skin, and can spread easily to the tissue under the skin.

Cellulitis can affect almost any part of your body (e.g., face, eye, arms and other areas). Most commonly, cellulitis occurs on the lower legs and in areas where the skin is damaged or inflamed allowing bacteria to enter. Anyone, at any age, can develop cellulitis. However, you are at increased risk if you smoke, have diabetes or poor circulation.

Left untreated, the infection can spread to your lymph nodes and bloodstream and rapidly become life-threatening. Prior to the development of antibiotics, cellulitis was fatal. With the introduction of antibiotics, most people recover fully within a week.

Cellulitis isn’t usually spread from person to person.

If you think you or someone in your care has cellulitis, it’s important to get medical attention soon as possible.

The main signs of cellulitis are skin that is red, painful, swollen, tender and warm to touch. People with severe cellulitis can get fever, chills, sweating and nausea, and might feel generally unwell.

Cellulitis often affects the lower leg, but can occur on any part of the body including the face. The infection may occur when bacteria enter the skin through an ulcer, cut or a scratch or an insect bite. However it can occur without any visible damage to the skin.

Sometimes bacteria from cellulitis spreads into the blood stream, which is called sepsis and this is a medical emergency.

People with cellulitis can quickly become very unwell and a small number of people may develop serious complications.

Antibiotics are the main treatment, usually orally at home. Some people need treatment in hospital. Rest and elevation (raising) of the limb are also very important. In some cases the affected limb may need compression.

Figure 1. Cellulitis leg

Figure 2. Cellulitis foot

Figure 3. Facial cellulitis

Who gets cellulitis?

Cellulitis affects people of all ages and races. Predispositions to cellulitis include:

• Previous episode(s) of cellulitis
• Fissuring of toes or heels, eg due to athlete’s foot, tinea pedis or cracked heels
• Venous disease, eg gravitational eczema, leg ulceration, and/or lymphoedema
• Current or prior injury, eg trauma, surgical wounds, radiotherapy
• Immunodeficiency, eg human immunodeficiency virus infection (HIV)
• Immune suppressive medications
• Diabetes
• Chronic kidney disease
• Chronic liver disease
• Obesity
• Pregnancy
• Alcoholism

Many people falsely attribute an episode of cellulitis to an unseen spider bite. Documented spider bites have not led to cellulitis.

Is cellulitis contagious?

Cellulitis isn’t usually spread from person to person. Cellulitis is an infection of the deeper layers of the skin most commonly caused by bacteria that normally live on the skin’s surface. You have an increased risk of developing cellulitis if you:

• Have an injury, such as a cut, fracture, burn or scrape
• Have a skin condition, such as eczema, athlete’s foot or shingles
• Participate in contact sports, such as wrestling
• Have diabetes or a weakened immune system
• Have a chronic swelling of your arms or legs (lymphedema)
• Use intravenous drugs

Reduce the risk of transmission

Cellulitis is spread by skin-to-skin contact or by touching infected surfaces. Stop the spread by:

• Washing your hands often.
• Bathing or showering daily.
• Do not let dressing become wet. If they do get wet they will need to be changed. Do not swim until infection clears up.
• Covering the wound with a gauze dressing (not a Band-Aid)
• Washing your bed linen, towels and clothing separately from other family members while the infection is healing.

Cellulitis may arise when skin injury or inflammation is not adequately treated.

How to clean a wound

You can look after most cuts and wounds yourself. You can:

• Stop any bleeding by holding a clean cloth or bandage on it and apply firm pressure. Use a clean towel to apply light pressure to the area until bleeding stops (this may take a few minutes). Minor cuts and scrapes usually stop bleeding on their own. Be aware that some medicines (e.g. aspirin and warfarin) will affect bleeding, and may need pressure to be applied for a longer period of time. If needed, apply gentle pressure with a clean bandage or cloth and elevate the wound until bleeding stops.
• Wash your hands well. Prior to cleaning or dressing the wound, ensure your hands are washed to prevent contamination and infection of the wound.
• Clean the wound by rinsing it with clean water and picking out any dirt (e.g. gravel) or debris with tweezers (don’t use antiseptic cream), as this will reduce the risk of infection. Keeping the wound under running tap water will reduce the risk of infection. Wash around the wound with soap.
• Dry the wound. Gently pat dry the surrounding skin with a clean pad or towel.
• Replace any skin flaps if possible. If there is a skin flap and it is still attached, gently reposition the skin flap back over the wound as much as possible using a moist cotton bud or pad.
• To help the injured skin heal, use an antibiotic ointment (e.g., Neosporin, Polysporin) or petroleum jelly to keep the wound moist. Petroleum jelly prevents the wound from drying out and forming a scab; wounds with scabs take longer to heal. This will also help prevent a scar from getting too large, deep or itchy. As long as the wound is cleaned daily, it is not necessary to use anti-bacterial ointments. However, several studies have supported the use of prophylactic topical antibiotics for minor wounds. An randomized controlled trial of 426 patients with uncomplicated wounds found significantly lower infection rates with topical bacitracin, neomycin/bacitracin/polymyxin B, or silver sulfadiazine (Silvadene) compared with topical petrolatum (5.5%, 4.5%, 12.1%, and 17.6%, respectively) ¹. Certain ingredients in some ointments can cause a mild rash in some people. If a rash appears, stop using the ointment.
• Cover the wound (small wounds can be left uncovered) ². Use a non-stick or gentle dressing and lightly bandage in place; try to avoid using tape on fragile skin to prevent further trauma on dressing removal. Dressings protect the wound by acting as a barrier to infection and absorbing wound fluid. A moist wound bed stimulates epithelial cells to migrate across the wound bed and resurface the wound ³. A dry environment leads to cell desiccation and causes scab formation, which delays wound healing. Older studies in animals and humans suggest that moist wounds had faster rates of re-epithelialization compared with dry wounds ⁴.
• Manage pain. Wounds can be painful, so consider pain relief while the wound heals. Talk to your doctor or pharmacist about options for pain relief.
• Change the dressing every day or whenever the bandage becomes wet or dirty.
• Get a tetanus shot. Get a tetanus shot if you haven’t had one in the past five years and the wound is deep or dirty.
• Watch for signs of infection. See a doctor if you see signs of infection on the skin or near the wound, such as redness, increasing pain, drainage, warmth or swelling.
• It’s also important to care for yourself, as this helps wounds heal faster. So eat fresh food, get some exercise, avoid smoking, and avoid drinking too much and drink plenty of water (unless you have liquid intake restrictions) to maintain supple, healthy skin.

See a doctor or nurse for a tetanus immunization within a day if you have had any cut or abrasion and any of the following apply:

• It is more than 10 years since your last tetanus shot or you can’t remember when you last had a tetanus shot ⁵. The Centers for Disease Control and Prevention (CDC) recommends that tetanus toxoid be administered as soon as possible to patients who have no history of tetanus immunization, who have not completed a primary series of tetanus immunization (at least three tetanus toxoid–containing vaccines), or who have not received a tetanus booster in the past 10 years.
• It is more than five years since your last tetanus shot and there was dirt in in the cut or abrasion, or the cut is deep.
• You should have the tetanus booster shot within 48 hours of the injury.
  • Besides a tetanus shot, your doctor may also give you an injection of something called tetanus immune globulin, which acts fast to prevent infection ⁶. There is a small window of opportunity for the tetanus immune globulin to work, so don’t delay seeking medical care.
  • Be aware of the first signs of tetanus infection. Also known as lockjaw, tetanus causes stiffness of the neck, difficulty swallowing, rigidity of abdominal muscles, spasms, sweating and fever. Symptoms usually begin eight days after the infection, but occur anywhere within three days to three weeks.

Cellulitis causes

Cellulitis occurs when bacteria, most commonly Streptococcus pyogenes (two thirds of cases) and Staphylococcus aureus (one third of cases), enter through a crack or break in your skin. The incidence of a more serious staphylococcus infection called methicillin-resistant Staphylococcus aureus (MRSA) is increasing.

Rare causes of cellulitis include:

• Pseudomonas aeruginosa, usually in a puncture wound of foot or hand
• Haemophilus influenzae, in children with facial cellulitis
• Anaerobes, Eikenella, Streptococcus viridans, due to human bite
• Pasteurella multocida, due to cat or dog bite
• Vibrio vulnificus, due to salt water exposure, e.g., coral injury
• Aeromonas hydrophila from fresh or salt water exposure, e.g., following leech bites
• Erysipelothrix (erysipeloid), in butchers

Cellulitis usually occurs in skin areas that have been damaged or inflamed for other reasons, including:

• trauma, such as an insect bite, burn, abrasion or cut
• a surgical wound
• skin problems, such as eczema, psoriasis, scabies or acne
• a foreign object in the skin, such as metal or glass.

Often, it is not possible to find a cause for cellulitis.

Although cellulitis can occur anywhere on your body, the most common location is the lower leg. Bacteria are most likely to enter disrupted areas of skin, such as where you’ve had recent surgery, cuts, puncture wounds, an ulcer, athlete’s foot or dermatitis.

Animal bites can cause cellulitis. Bacteria can also enter through areas of dry, flaky skin or swollen skin.

Risk factors for developing cellulitis

Several factors put you at increased risk of cellulitis:

• Injury. Any cut, fracture, burn or scrape gives bacteria an entry point.
• Weakened immune system. Conditions that weaken your immune system — such as diabetes, leukemia and HIV/AIDS — leave you more susceptible to infections. Certain medications also can weaken your immune system.
• Skin conditions. Conditions such as eczema, athlete’s foot and shingles can cause breaks in the skin, which give bacteria an entry point.
• Chronic swelling of your arms or legs (lymphedema). This condition sometimes follows surgery.
• History of cellulitis. Having had cellulitis before makes you prone to develop it again.
• Obesity. Being overweight or obese increases your risk of developing cellulitis.

Cellulitis prevention

If your cellulitis recurs, your doctor may recommend preventive antibiotics. To help prevent cellulitis and other infections, take these precautions when you have a skin wound:

• Wash your wound daily with soap and water. Do this gently as part of your normal bathing.
• Apply a protective cream or ointment. For most surface wounds, an over-the-counter ointment (Vaseline, Polysporin, others) provides adequate protection.
• Cover your wound with a bandage. Change bandages at least daily.
• Watch for signs of infection. Redness, pain and drainage all signal possible infection and the need for medical evaluation.

People with diabetes and those with poor circulation need to take extra precautions to prevent skin injury. Good skin care measures include the following:

• Inspect your feet daily. Regularly check your feet for signs of injury so you can catch infections early.
• Moisturize your skin regularly. Lubricating your skin helps prevent cracking and peeling. Do not apply moisturizer to open sores.
• Trim your fingernails and toenails carefully. Take care not to injure the surrounding skin.
• Protect your hands and feet. Wear appropriate footwear and gloves.
• Promptly treat infections on the skin’s surface (superficial), such as athlete’s foot. Superficial skin infections can easily spread from person to person. DON’T wait to start treatment.

How to prevent recurrent episodes of cellulitis

To help prevent recurrent episodes of cellulitis — a bacterial infection in the deepest layer of skin — keep skin clean and well-moisturized. Prevent cuts and scrapes by wearing appropriate clothing and footwear, using gloves when necessary, and trimming fingernails and toenails with care.

Factors that may increase your risk of cellulitis include:

• Pre-existing skin diseases, such as athlete’s foot
• Puncture injuries, such as insect or animal bites
• Surgical incisions or pressure sores
• Immune system problem, such as diabetes
• Injuries that occur when you’re in a lake, river or ocean
• Hot tub use

Cellulitis usually makes the affected skin hot, red, swollen and painful. Your skin may look pebbled, like an orange peel. Seek prompt medical attention at the first sign of a skin infection. Treatment is usually with antibiotics. Some people who frequently develop cellulitis may benefit from long-term antibiotic treatment to prevent recurrent infections.

Cellulitis symptoms

Possible signs and symptoms of cellulitis, which usually occur on one side of the body, include:

• Redness, swelling and tenderness of skin and subcutaneous tissue underneath it that tends to expand (spread)
• Warmth of the affected skin
• Fever and chills
• Swollen glands or lymph nodes
• Pain
• Red spots
• Blisters
• Dimpled skin (peau d’orange)
• Weeping or leaking of yellow clear fluid or pus
• Erosions and ulceration
• Abscess formation
• Purpura: petechiae, ecchymoses, or haemorrhagic bullae

Cellulitis may be associated with lymphangiitis and lymphadenitis, which are due to bacteria within lymph vessels and local lymph glands. A red line tracks from the site of infection to nearby tender, swollen lymph glands.

Left untreated, cellulitis can rapidly turn into a life-threatening condition. Treatment usually includes antibiotics. In severe cases, you may need to be hospitalized and receive antibiotics through your veins (intravenously).

Cellulitis complications

The infection can spread to the rest of the body. The lymph nodes may swell and be noticed as a tender lump in the groin and armpit. You may also have fevers, sweats and vomiting.

Severe or rapidly progressive cellulitis may lead to:

• Necrotizing fasciitis (a more serious soft tissue infection recognized by severe pain, skin pallor, loss of sensation, purpura, ulceration and necrosis). Necrotizing fasciitis is an example of a deep-layer infection. It’s an extreme emergency.
• Gas gangrene
• Severe sepsis (blood poisoning)
• Infection of other organs, e.g., pneumonia, osteomyelitis, meningitis
• Endocarditis (heart valve infection).

Sepsis is recognized by fever, malaise, loss of appetite, nausea, lethargy, headache, aching muscles and joints. Serious infection leads to hypotension (low blood pressure, collapse), reduced capillary circulation, heart failure, diarrhea, gastrointestinal bleeding, renal failure and loss of consciousness.

Recurrent episodes of cellulitis may damage the lymphatic drainage system and cause chronic swelling of the affected limb.

Cellulitis diagnosis

Your doctor will likely be able to diagnose cellulitis by looking at your skin. In some cases, he or she may suggest blood tests or other tests to help rule out other conditions.

Investigations may reveal:

• Leukocytosis (raised white cell count).
• Elevated C-reactive protein (CRP)
• Causative organism, on culture of blood or of pustules, crusts, erosions or wound

Imaging may be performed. For example:

• Chest X-ray in case of heart failure or pneumonia
• Doppler ultrasound to look for blood clots (deep vein thrombosis)
• MRI in case of necrotizing fasciitis.

Cellulitis treatment

Antibiotics are used to treat the infection. Oral antibiotics may be adequate, but in the severely ill person, intravenous antibiotics will be needed to control and prevent further spread of the infection. This treatment is given in hospital or sometimes, at home by a local doctor or nurse. Your doctor also might recommend elevating the affected area, which may speed recovery.

Within three days of starting an antibiotic, let your doctor know whether the infection is responding to treatment. You’ll need to take the antibiotic for as long as your doctor directs, usually five to 10 days but possibly as long as 14 days. After successful treatment, the skin may flake or peel off as it heals. This can be itchy.

As the infection improves, you may be able to change from intravenous to oral antibiotics, which can be taken at home for a further week to 10 days. Most people respond to antibiotics in two to three days and begin to show improvement. In some cases, antibiotics are continued until all signs of infection have cleared (redness, pain and swelling), sometimes for several months.

In most cases, signs and symptoms of cellulitis disappear after a few days. You may need to be hospitalized and receive antibiotics through your veins (intravenously) if:

• Signs and symptoms don’t respond to oral antibiotics
• Signs and symptoms are extensive
• You have a high fever

In rare cases, the cellulitis may progress to a serious illness by spreading to deeper tissues. In addition to broad spectrum antibiotics, surgery is sometimes required.

Treatment should also include:

• Analgesia to reduce pain
• Adequate water/fluid intake
• Management of co-existing skin conditions like venous eczema or tinea pedis

Cellulitis antibiotics

The management of cellulitis is becoming more complicated due to rising rates of methicillin-resistant Staphylococcus aureus (MRSA) and macrolide- or erythromycin-resistant Streptococcus pyogenes.

Usually, doctors prescribe a drug that’s effective against both streptococci and staphylococci. It’s important that you take the medication as directed and finish the entire course of medication, even after you feel better.

Treatment of cellulitis with systemic illness

More severe cellulitis and systemic symptoms should be treated with fluids, intravenous antibiotics and oxygen. The choice of antibiotics depends on local protocols based on prevalent organisms and their resistance patterns, and may be altered according to culture/susceptibility reports.

• Penicillin-based antibiotics are often chosen (eg penicillin G or flucloxacillin)
• Amoxicillin and clavulanic acid provide broad-spectrum cover if unusual bacteria are suspected
• Cephalosporins are also commonly used (eg ceftriaxone, cefotaxime or cefazolin)
• Clindamycin, sulfamethoxazole/trimethoprim, doxycycline and vancomycin are used in patients with penicillin or cephalosporin allergy, or where infection with methicillin-resistant Staphylococcus aureus is suspected
• Broad-spectrum antibiotics may also include linezolid, ceftaroline, or daptomycin

Sometimes oral probenecid is added to maintain antibiotic levels in the blood.

Treatment may be switched to oral antibiotics when fever has settled, cellulitis has regressed, and CRP is reducing.

Cellulitis home treatment

Self-care at home to help ease any pain and swelling include:

• Get plenty of rest. This gives your body a chance to fight the infection.
• Raise the area of the body involved as high as possible. This will ease the pain, help drainage and reduce swelling.
• Take pain-relieving medication such as paracetamol. Check the label for how much to take and how often. The pain eases once the infection starts getting better.
• If you are not admitted to hospital, you will require a follow-up appointment with your doctor within a day or two to make sure the cellulitis is improving. This appointment is important to attend.

Management of recurrent cellulitis

Patients with recurrent cellulitis should:

• Avoid trauma, wear long sleeves and pants in high risk activities, eg gardening
• Keep skin clean and well moisturized, with nails well tended
• Avoid having blood tests taken from the affected limb
• Treat fungal infections of hands and feet early
• Keep swollen limbs elevated during rest periods to aid lymphatic circulation. Those with chronic lymphedema may benefit from compression garments.

Patients with 2 or more episodes of cellulitis may benefit from chronic suppressive antibiotic treatment with low-dose penicillin V or erythromycin, for one to two years.

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