What Is It?
Cellulitis is a serious bacterial infection of the skin. Bacteria break through the skin's protective outer layer, typically at the site of an injury, such as a cut, puncture, sore, burn or bite. Cellulitis can occur at the site of surgery, or where there is a catheter. Once beneath the skin surface, bacteria multiply and make chemicals that cause inflammation in the skin.
Cellulitis that is not caused by a wound or catheter most often occurs on the legs and feet. However, it can develop on any part of the body, including the trunk, arms and face. It often develops where there is edema (swelling), poor blood flow, or a skin rash that creates breaks in the skin, such as a fungus infection between the toes (athlete's foot).
Many types of bacteria can cause cellulitis. Most cases are caused by Streptococcus pyogenes (strep) or Staphylococcus aureus (staph). During the last several years, it has become more common for a strain of drug-resistant bacteria to cause cellulitis. This bacteria is named community-acquired methicillin-resistant staphylococcal aureus, or "community-acquired MRSA." Infections with this type of bacteria can lead to blistering of the skin or deep, more serious infections.