Cellulitis on the leg of a 75 year old woman with varicose eczema (dark regions), a skin inflammation (dermatitis) caused by poor blood circulation in the veins. Cellulitis (red) is a bacterial infection of the skin and its underlying tissues. It is often due to infection by Streptococcus bacteria that enter through a wound or break in the skin. Cellulitis may cause a fever and chills, and, if left untreated, may result in septicaemia (blood poisoning) or gangrene. It is usually treated with antibiotic drugs.