Familial eosinophilic cellulitis is a rare eosinophilic disorder characterized by itchy, burning, red, and inflamed areas on the skin. These rashes often appear on the lower arm or leg. The lesions may be single or multiple. They are usually red at first (looking like cellulitis) then change from brown-red, to blue-gray, and then to greenish-gray. The lesions are usually painful and are sometimes associated with a fever. They typically heal without scarring within weeks to months, however they often recur. The cause of familial eosinophilic cellulitis is unknown, but some researchers think that it is an autoimmune reaction.