Uncomplicated cellulitis begins with a small area of skin that's red, glossy, painful, and warm to the touch, typically around a cut. It most often strikes the lower leg, but the arms, hands, feet, and groin are other likely sites.
Some types of bacteria can get into the lymphatic system, a network of tubes and nodes that carry disease-fighting cells and waste matter around the body. If this happens, the infection can travel under the skin and spread to other parts of the body.
Another type of cellulitis is erysipelas. The inflamed skin in erysipelas is not smooth but raised, often completely separated from the layer beneath by a pocket of gas created by the bacteria. There's often a fever a day or two before the rash.
The most severe complications of cellulitis are meningitis and blood poisoning (if the bacteria get into the bloodstream, called bacteremia). Meningitis can occur if the bacteria get inside the central nervous system (e.g., brain or spinal cord). The most likely route is through the eye socket. Cellulitis around an eyelid is called preseptal cellulitis. It causes a rash that might be painful or itchy. If the bacteria get behind the seal where the eye meets its socket, the condition is called orbital cellulitis. This is a medical emergency that causes symptoms of fever and impaired vision. It requires immediate treatment to prevent meningitis or eye damage.
If the infection gets into the lymphatic system or the bloodstream, red lines may be seen under the skin before the main rash appears. This may cause symptoms like fever, sweats, and nausea.