The eggs of body lice are laid on clothing fibers and occasionally on human body hairs. Under normal conditions the eggs will hatch in seven to 11 days. The young lice which escape from the egg must feed within 24 hours or they will die. Newly hatched lice will periodically take blood meals and molt three times before becoming sexually mature adults. Adults range in color from white to brown to dark gray.
Adults can only survive one to two days without a blood meal.
The nymphs and adults all have piercing-sucking mouthparts which pierce the skin for a blood meal. The reaction of individuals to louse bites can vary considerably. Persons previously unexposed to lice experience little irritation from their first bite. After a short time individuals may become sensitized to the bites, and may react with a general allergic reaction including reddening of the skin, itching, and overall inflammation. Both the immature or nymphal forms and adult lice feed on human blood.