Cellulitis is a skin infection caused by bacteria entering the skin. The most common bacteria that cause cellulitis include:
- Group A ß – hemolytic streptococcus (Strep)
- Streptococcus pneumoniae (Strep)
- Staphylococcus aureus (Staph)
Staph and strep bacteria are commonly found on the skin and mucous membranes of the mouth and nose in healthy people. The bacteria may enter the body through a break in the skin, such as a cut, scrape, burn, or wound.
Other causes may include human or animal bites, or injuries that happen in water. Cellulitis can also occur as a complication of other conditions, such as eczema or athlete’s foot. The incidence of a more serious staphylococcus infection called methicillin-resistant Staphylococcus aureus (MRSA) is increasing. Cellulitis can occur anywhere on the body, but the most common location is the lower leg.
Risk factors
Several factors increase the risk of cellulitis:
- Injury. Any cut, fracture, burn or scrape gives bacteria an entry point.
- Weakened immune system. Conditions that weaken the immune system — such as diabetes, leukemia and HIV/AIDS — increase the risk of infection. Certain medications also can weaken the immune system.
- Skin conditions. Conditions such as atopic dermatitis (eczema), athlete’s foot and shingles can cause breaks in the skin, which give bacteria an entry point.
- Long-term (chronic) swelling of the arms or legs (lymphedema). This condition sometimes happens after surgery.
- History of cellulitis. Having had cellulitis before increases the risk of getting it again.
- Being overweight. Excess weight increases the risk of developing cellulitis.
It is important to seek medical treatment if you suspect you have cellulitis, as it can spread and become serious if left untreated.