A variety of human parasites have some limited medicinal uses. Leeches can be used to control bleeding or to draw toxins out of the bloodstream. Certain intestinal worms can aid in the treatment of autoimmune disorders. Pediculus capitis, an animal commonly referred to as the head louse, however, cannot be used medicinally. The infestation of a human host by this parasite is known as pediculosis capitis and is not usually an emergency, though heavy infestations can seriously damage the skin and cause the loss of a considerable amount of blood.
Pediculus capitis can cause severe irritation to the skin. Head lice are insects that hook onto the scalp and hair follicles and feed on a person's blood. In order to get at a person's blood, a louse must bite a small hole in the skin. An enzyme in the louse's saliva makes it difficult for the blood to clot, so the louse can continue to feed through a single bite for a long period of time. The hooked legs of the louse, the bite, and the saliva released into the bite can cause irritation and make a the scalp itch.
A medical condition that requires treatment, pediculosis capitis is seen frequently around the world and often affects children. It is passed from person to person through direct head to head contact or by sharing hoods, jackets, or scarves. Though treatment is still needed, the presence of a few lice on a person's head can often be taken care of without a visit to a doctor.
In order to treat pediculosis capitis, a number of steps must be followed. First, the person's bedding and clothing should be washed to kill any lice or nits that are on these fabrics. Afterward, the person should wash with a shampoo that contains an insecticide designed to kill lice. Natural treatments, many of which are quite effective, can also be used. Nits and adult lice can also be removed with a special comb.
Though it is extremely unlikely, an infestation of pediculus capitis can lead to other medical conditions. Sores on the scalp are the most common complication of these infestations, especially if a person scratches excessively. Left untreated, it is possible to develop a bacterial infection in these sores. Pediculus capitis infestations do not, however, spread blood borne diseases.