Cellulitis is an acute inflammation of the connective tissue of the skin, caused by infection with staphylococcus, streptococcus or other bacteria (see also Erysipelas).

The skin normally has many types of bacteria living on it, but intact skin is an effective barrier that keeps these bacteria from entering and growing within the body. When there is a break in the skin, however, bacteria can enter the body and grow there, causing infection and inflammation. The skin tissues in the infected area become red, hot, irritated and painful.

Cellulitis is most common on the lower legs and the arms or hands, although other areas of the body may sometimes be involved. If it involves the face (erysipelas), medical attention is urgent. People with fungal infections of the feet, who have skin cracks in the webspaces between the toes, may have cellulitis that keeps coming back, because the cracks in the skin offer an opening for bacteria.

Risk factors for cellulitis include:

• Insect bites and stings, animal bite, or human bite
• Injury or trauma with a break in the skin (skin wounds)
• History of peripheral vascular disease
• Diabetes -related or ischemic ulcers
• Cracks or peeling skin between the toes
• Use of immunosuppressive or corticosteroid medications

• Localized skin redness or inflammation that increases in size as the infection spreads
• Tight, glossy, "stretched" appearance of the skin
• Pain or tenderness of the area
• Skin lesion or rash (macule):
  • Sudden onset
  • Usually with sharp borders
  • Rapid growth within the first 24 hours
• Warmth over the area of redness
• Fever
• Other signs of infection:
  • Chills, shaking
  • Warm skin, sweating
  • Fatigue
  • Muscle aches, pains (myalgias)
  • General ill feeling (malaise)

• Nausea and vomiting
• Joint stiffness caused by swelling of the tissue over the joint
• Hair loss at the site of infection

During a physical examination, the doctor may find localized swelling. Occasionally, swollen glands (lymph nodes) can be detected near the cellulitis. Your health care provider may mark the edges of the redness with a pen, to see if the redness extends beyond the marked border over the next several days.

Tests that may be used:

• A CBC may show an elevated white blood cell count, and indicates a bacterial infection.
• A blood culture may be performed if generalized infection is suspected.

Cellulitis treatment may require hospitalization if it is severe enough to warrant intravenous antibiotics and close observation. At other times, treatment with oral antibiotics and close outpatient follow-up is enough. Treatment is focused on control of the infection and prevention of complications.

Antibiotics are given to control infection, and analgesics may be needed to control pain.

Elevate the infected area, usually higher than the heart, to minimize swelling. Rest until symptoms improve.

Cure is possible with 7 to 10 days of treatment. Cellulitis may be more severe in people with chronic diseases and people who are susceptible to infection (immunosuppressed).

• Tissue death (gangrene)
• Sepsis, generalized infection and shock
• Meningitis (if cellulitis is on the face)
• Lymphangitis (inflammation of the lymph vessels)

Call your health care provider if symptoms indicate that cellulitis may be present. Seek medical attention urgently if it appears to involve the face.

Call your health care provider if you are being treated for cellulitis and new symptoms develop, such as persistent fever, drowsiness, lethargy, blistering over the cellulitis, or extension of the red streaks.

Avoid skin damage by wearing appropriate protective equipment when participating in work or sports. Also, clean any breaks in the skin carefully and watch for redness, pain, drainage, or other signs of infection.

Finally, maintain good general health and control chronic medical conditions. A body that is healthy can more easily fight bacteria before they multiply and cause infection, while a body that is run down has less protection against infection.