– A diffuse, spreading, acute inflammation and infection of the skin and subcutaneous tissues.

Causes and Incidence

The most common cause of cellulitis is infection with Streptococcus pyogenes or Staphylococcus aureus after a break in the skin. It also can be caused by infection with gram-negative bacilli associated with diabetic foot ulcers, or by various bacteria introduced by animal or insect bites.

Disease Process

A break in the skin caused by trauma, ulceration, or lymphedema is invaded by a pathogen, setting up an inflammatory and infectious process. The infection spreads because the pathogen produces enzymes capable of breaking down the cellular components that usually wall off and contain the inflammation.


Local redness, swelling, and tenderness, usually of the lower extremities, are the most common presenting symptoms. The skin is hot to the touch and may have an orange peel–like appearance and texture. Red streaks may extend from indistinct borders, and purulent discharge may be present. Occasionally systemic manifestations develop, such as chills, fever, headache, and tachycardia.

Potential Complications

Rare complications include severe necrotizing subcutaneous infection with gangrene and permanent damage to the lymphatic system.

Diagnostic Tests

The diagnosis is made by clinical examination.


Incision and drainage of abscesses; debridement of necrotic tissue.

Antiinfective drugs to treat infection; analgesics for pain.

Immobilization and elevation of affected area to reduce edema; cool, wet dressings to relieve pain.