Lice Infestation
Lice infestation (pediculosis) is a skin infestation by tiny wingless insects.
 See the figure A Close-up Look at Lice.
Lice are barely visible wingless insects that spread easily from person to person by body contact and shared clothing and other personal items. Three species of lice inhabit different parts of the body.
Head lice infest the scalp hair. The infestation is spread by personal contact and possibly by shared combs, brushes, hats, and other personal items. Head lice are a common scourge of school children of all social strata. Head lice are less common among blacks.
Body lice usually infest people who have poor hygiene and those living in close quarters or crowded institutions. They live in the seams of garments that are in contact with the skin.
Pubic lice ("crabs"), which infest the genital area, are typically spread during sexual contact. These lice may infest the chest hair, underarm hair, beard hair, eyebrows, and eyelashes as well.
Symptoms and Diagnosis
Lice infestation causes severe itching in the infested area. Intense scratching often breaks the skin, which can lead to bacterial infections. Children may hardly notice head lice or may have only a vague scalp irritation.
Lice themselves are sometimes hard to find, but their eggs are readily apparent. Female lice lay shiny grayish white eggs (nits) that can be seen as tiny globules firmly stuck to hairs near their base. With chronic scalp infestations, the nits grow out with the hair and therefore can be found some distance from the scalp, depending on the duration of the infestation.
Nits are distinguished from other foreign material present on hair shafts by the fact that they are so strongly attached. Adult body lice and their eggs also may be found in the seams of clothing worn close to the skin.
Treatment
Several effective prescription and nonprescription drugs are available to treat lice. Nonprescription shampoos and creams containing pyrethrins plus piperonyl butoxide are applied for 10 minutes and are then rinsed out. Prescription permethrin, applied as a liquid or as a cream, is also effective. Lindane--a prescription drug that can be applied as a cream, lotion, or shampoo--also cures lice infestation but is not as effective as the other preparations and is not recommended for children because of possible neurologic side effects. Prescription malathion, although highly effective at killing both adult lice and eggs, is not considered a first line of treatment because it is flammable, has an objectionable odor, and must remain on the skin for 8 to 12 hours. All louse treatments are repeated in 7 to 10 days to kill newly hatched lice.
After a drug application, nits must be removed manually, because drugs do not kill all nits and because it is not possible to distinguish between living and dead nits. Removal requires a fine-tooth comb--which is often packaged with the medication--and careful searching (hence the term "nit-picking"). Because the nits are so strongly stuck to the hair, several nonprescription preparations are available to loosen them. The nits of body lice are destroyed simply by throwing away infested clothing.
Sources of infestation (combs, hats, clothing, and bedding) should be decontaminated by laundering or dry cleaning.
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