Lice Infestation Health Article

Diagnosis

Doctors can diagnose lice infestations from looking closely at the parts of the body where the patient has been scratching. Lice are large enough to be easily seen with the naked eye or a magnifying glass. The eggs of pubic lice as well as head lice can often be found by looking at the base of the patient's hairs. Pediatricians are most likely to diagnose lice in school-age children.

It is important for doctors to rule out other diseases that can cause scratching and skin inflammation because the medications used to kill lice are very strong and can have bothersome side effects. The doctor will need to distinguish between head lice and dandruff; between body lice and scabies (a disease caused by skin mites); and

between pubic lice and eczema. Blood tests or other laboratory tests are not useful in diagnosing lice infestations.

Treatment

Lice infestations are treated with externally applied medications that either kill the lice or prevent them from feeding. Cases of head lice are usually treated with shampoos or rinses containing either lindane (Kwell) or permethrin (Nix). Because lindane is absorbed through the skin, the person giving the application should wear rubber gloves and rinse the patient's hair or body completely after use. Following the treatment, nits should be removed from the hair with a fine-toothed comb or tweezers. Lindane is also effective for treating infestations of body or pubic lice, but it should not be used by pregnant women. In most cases one treatment is sufficient, but the medication can be reapplied a week later if living lice have reappeared.

Infestations of body lice can also be treated by washing the patient's clothes or bedding in boiling water, ironing seams with an iron on a high setting, or treating the clothes with 1% malathion powder or 10% DDT powder.

If the patient's eyelashes have been infested, the only safe treatments are either a thick coating of petroleum jelly (Vaseline) applied twice daily for eight days, or 1% yellow oxide of mercury applied four times a day for two weeks. Any remaining nits should be removed with tweezers.

Patients with pubic lice should be examined and tested for other STDs.

Alternative treatment

For pubic lice, some practitioners of holistic medicine recommend a mixture of 25% oil of pennyroyal (Mentha pulegium), 25% garlic (Allium sativum) oil, and

50% distilled water applied three times in a three-day period, followed by removal of dormant eggs to prevent reinfestation.

Prognosis

Lice can be successfully eradicated in almost all cases, although some cases of lindane-resistant lice have been reported. In general, patients are more at risk from typhus and other diseases spread by lice than from the lice themselves.

Prevention

There are no vaccines or skin treatments that will protect a person against lice prior to contact. In addition, lice infestation does not provide immunity against rein-fection; recurrences are in fact quite common. Prevention depends on adequate personal hygiene at the individual level and the following public health measures:

• teaching school-age children the basics of good personal hygiene, including the importance of not lending or borrowing combs, brushes, or hats
• notifying and treating an adult patient's close personal and sexual contacts
• examining homeless people, elderly patients incapable of self-care, and other high-risk individuals prior to hospital admission for signs of louse infestation. This measure is necessary to protect other hospitalized people from the spread of lice

BOOKS

Berger, Timothy G. "Skin and Appendages." In Current Medical Diagnosis and Treatment, 1996. 35th ed. Ed. Stephen McPhee, et al. Stamford: Appleton & Lange, 1995.

"Dermatologic Disorders: Parasitic Infections of the Skin." In The Merck Manual of Diagnosis and Therapy. 16th ed. Ed. Robert Berkow. Rahway, NJ: Merck Research Laboratories, 1992.

"Lindane." In Nurses Drug Guide 1995, ed. Billie Ann Wilson, et al. Norwalk, CT: Appleton & Lange, 1995.

McCarthy, James S., and Thomas B. Nutman. "Parasitic Diseases of the Skin." In Conn's Current Therapy, 1996,ed. Robert E. Rakel. Philadelphia: W. B. Saunders Co., 1996.

Millikin, Larry E. "Flies, Lice, Mites, and Bites." In Current Diagnosis. Vol. 9. Ed. Rex B. Conn, et al. Philadelphia: W.B. Saunders Co., 1997.

Morelli, Joseph G., and William L. Weston. "Skin." In Current Pediatric Diagnosis & Treatment, ed. William W. Hay Jr., et al. Stamford: Appleton & Lange, 1997.

"Permethrin." In Nurses Drug Guide 1995, ed. Billie Ann Wilson, et al. Norwalk, CT: Appleton & Lange, 1995.

Rebecca J. Frey, Ph.D.