Cellulitis is an inflammation of the connective tissue underlying the skin, that can be caused by a bacterial infection. This condition can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken, cracks in the skin, cuts, blisters, burns, insect bites, surgical wounds, or sites of intravenous catheter insertion.

The mainstay of therapy, is treatment with appropriate antibiotics.

Skin on the face or lower legs is most commonly affected by this infection, though the inflamation can occur on any part of the body. Symptoms may be superficial — affecting only the surface of the skin — but may also affect the tissues underlying the skin, and can spread to the lymph nodes and bloodstream.

It is unrelated to cellulite, a cosmetic condition featuring dimpling of the skin.


Causes

Cellulitis is caused by a type of bacteria entering by way of a break in the skin. This break need not be visible. Group A streptococcus and staphylococcus are the most common of these bacteria, which are part of the normal flora of the skin but cause no actual infection until the skin is broken. Predisposing conditions for cellulitis include insect bite, animal bite, pruritic skin rash, recent surgery, athlete's foot, dry skin, eczema, burns and boils, though there is debate as to whether minor foot lesions contribute.


Symptoms

Early symptoms may include fever, headache, nausea. and redness. These signs of redness on the affected area can develop in as little as twenty-four hours or can take days to develop.

Cellulitis is characterized by redness, swelling, warmth, and pain or tenderness. and frequently occurs on exposed areas of the body such as the arms, legs, and face. Other symptoms can include fever or chills and headaches. In advanced cases , red streaks (sometimes described as 'fingers') may be seen traveling up the affected area. The swelling can spread rapidly.

This reddened skin or rash may signal a deeper, more serious infection of the inner layers of skin. Once below the skin, the bacteria can spread rapidly, entering the lymph nodes and the bloodstream and spreading throughout the body.

In rare cases, the infection can spread to the deep layer of tissue called the fascial lining. Necrotizing fasciitis, also called by the media "flesh-eating bacteria", is an example of a deep-layer infection. It represents an extreme medical emergency.


Diagnosis

The appearance of the skin will help a doctor make a diagnosis. The doctor may also suggest blood tests, a wound culture or other tests to help rule out a blood clot deep in the veins of the legs. inflamation and swelling in the lower leg is characterized by signs and symptoms that may be similar to those of a clot occurring deep in the veins, such as warmth, pain and swelling.

Clinical diagnosis is often the diagnosis for cellulitis, and local cultures do not always identify the causative organism. Blood cultures usually are positive only if the patient develops generalised sepsis. Conditions that may resemble cellulitis include deep vein thrombosis, which can be diagnosed with a compression leg ultrasound, and stasis dermatitis, which is inflammation of the skin from poor blood flow.


Treatment

Antibiotics - typically a combination of intravenous and oral antibiotics are administered. Bed rest and elevation of affected limbs is also recommended. Often physicians suggest patients drink plenty of fluids as well.


Duration

In many cases, the inflamation, infection, tenderness and swelling takes less than a week to disappear with antibiotic therapy. However, it can take months to resolve completely in more serious cases, and can result in severe debility or even death if untreated. If it is not properly cured it may appear to improve but can resurface again even after months and years.


Risk Factors

The elderly and those with weakened immune systems are especially vulnerable to contracting this condition. Diabetics are more susceptible to cellulitis than the general population because of impairment of the immune system; they are especially prone to cellulitis in the feet because the disease causes impairment of blood circulation in the legs leading to foot ulcers that commonly become infected.

Immunosuppressive drugs, HIV, and other illnesses or infections that weaken the immune system are also factors that make infection more likely. In addition, chickenpox and shingles often result in blisters which break, providing a gap in the skin through which bacteria can enter. Lymphedema, which causes swelling on the arms and/or legs, can also put an individual at risk.

Diseases that affect blood circulation in the legs and feet, such as chronic venous insufficiency and varicose veins, are also risk factors .

Cellulitis is also extremely prevalent amongst dense populations sharing hygiene facilities and common living quarters. Military installations which require communal showers provide such an environment, as it is prevalent among many recruits going through boot camp.


Prevention

Good hygiene and good wound care lower the risk of cellulitis. Any wounds should be cleaned and dressed appropriately. Changing bandages daily or when they become wet or dirty will reduce the risk of contracting cellulitis. Medical advice should be sought for any wounds which are deep, dirty or if there is concern about retained foreign bodies.

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