Healthline notes that cellulitis is caused by bacteria when they enter through a crack or cut in the skin. It is commonly caused by streptococcus and staphylococcus bacteria. Cellulitis first appears as a red, swollen area that is tender and painful to touch, and it often spreads rapidly.
Healthline reveals that 50 to 60 percent of cellulitis cases are caused by skin injuries, which can result from bites, skin piercing, a new tattoo or surgery. Risk factors of an infection include a weak immune system, intravenous drug use and skin conditions, such as eczema and fungal infection. Mayo Clinic notes that cellulitis is common in the lower leg but can occur in any part of the body. WebMD notes that antibiotics are used to treat cellulitis.