Cellulitis is more serious than the redness you commonly see surrounding an infected skin lesion. Cellulitis is an acute, but noncontagious, inflammation of the connective tissue beneath the surface of the skin. It is more wide-spread than a localized infection as seen in an ulcer or abscess. It causes the skin tissues in the infected area to become red, hot, painful and swollen. It can result from staphylococcus, streptococcus, or other bacterial infection. Intact skin is an effective barrier that normally keeps bacteria from entering and growing within the body. When there is a break in the skin, bacteria can enter causing infection and inflammation. Cellulitis is most common on the lower legs although skin on other areas of the body may be involved. The risk factors for cellulitis include insect bites and stings, animal or human bite and injury or trauma resulting in a break in the skin. Conditions which increase the chance of infection included history of peripheral vascular disease, diabetes mellitus, or ischemic ulcers; recent invasive medical or dental procedures; and the use of immunosuppressive medications.

Occasionally, streptococci can invade deeper structures with very rapid progression. When the fascia, the tissue overlying the muscle, becomes infected and dies, the disease is called necrotizing fasciitis. This has been called an infection with "flesh-eating bacteria". The reason some people develop this life-threatening infection while others only develop cellulitis is not entirely clear. Part of the reason has to do with the strain of bacteria involved. Certain strains of strep can produce toxins that destroy tissue and cause severe illness.

Avoid damage to your skin by wearing appropriate protective clothing and equipment as necessary. Treat any breaks in the skin by careful washing and a topical antibiotic. Watch closely for evidence of infection like redness, pain or drainage.