Adult head lice are about 1/8 inch long. Hatching occurs 7 to 10 days after attachment. Since lice go through a gradual metamorphosis, the tiny nymphs resemble adults. They grow to maturity in about 10 days.
Lice live on the scalp. They are able to crawl on the scalp between hairs with more speed than may be expected. Head lice suck blood painlessly by piercing the skin with sharp, needle-like mouth parts. Head lice neatly glue their eggs (called nits) to the hair shaft. The tiny, pearl-like eggs stick on to the hair so tightly that they can be dislodged only by being torn from the hair shaft by fingernails or a fine-toothed comb. Nits found within ¼ inch of the scalp indicate an active infestation.
Head lice spread from host to host through direct physical contact with an infested individual or by indirect contact such as sharing a comb, brush, hat or hair accessory with an infested individual or by storing a coat or hat infested with one or more head lice together with coats or hats of other persons. Transmission of lice is most common among siblings that have their hair brushed with a "family brush" or children who use hats and brushes of friends. Louse infestations are often discovered by school teachers who are watching for the signs of itching heads. However, classroom neighbors are not as likely to be infested as are brothers and sisters or close friends that sleep over or share brushes.
Several over-the-counter and prescription preparations are used to eliminate head louse infestations. Advise clients to contact health or medical personnel for recommendations concerning insecticidal shampoos and other preventative measures for the home. Advice regarding treatment of bacterial infections that can result from intense scratching during extensive infestations should be made by health care professionals.
In public areas, advise staff to:
Reported louse infestations should be investigated by an individual trained to perform head lice examinations. If live lice are not seen, the placement of nits on the hair shafts within ¼ inch of the scalp can serve to indicate a current infestation.