What is cellulitis?
Cellulitis is a bacterial infection of the skin and tissues beneath the skin. Unlike impetigo, which is a very superficial skin infection, cellulitis is a bacterial skin infection that also involves the skin's deeper layers: the dermis and subcutaneous tissue.
The main bacteria responsible for cellulitis are Streptococcus and Staphylococcus ("staph"), the same bacteria that can cause impetigo and other diseases. MRSA (methicillin-resistant Staph aureus) can also cause cellulitis. Sometimes, other bacteria (for example, Hemophilus influenzae, Pneumococcus, and Clostridium species) may cause cellulitis as well.
Cellulitis is fairly common and affects people of all races and ages. Men and women appear to be equally affected. Although cellulitis can occur in people of any age, it is most common in middle-aged and elderly people. Cellulitis is not contagious.