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 face and lower legs, although skin on other areas of the body may sometimes be involved.

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
• Recent cardiovascular, pulmonary (lung), dental or other procedures
• 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.

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.

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

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.