Fleas.

While more than 2,000 species and subspecies of fleas are known, only nine have significant medical and veterinary importance, and only six involve man. Eggs drop easily from pet hosts to be widely distributed throughout the home. Human flea bites range from small red welts to severe rash and itching; they are usually found only on wrists, ankles and legs. Treatment is symptomatic. Control of flea infestation is based on knowledge of the life cycle of the insect.