Head Lice

  • Medical Author:

    Dr. Eddie Hooker is currently an Assistant Professor in the Department of Health Services Administration at Xavier University in Cincinnati, Ohio. He is also an Associate Clinical Professor in the Department of Emergency Medicine at the University of Louisville and at Wright State University. His areas of expertise include emergency medicine, epidemiology, health-services management, and public health.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Quick GuideLice & Nits: How to Get Rid of Head Lice

Lice & Nits: How to Get Rid of Head Lice

What do head lice look like? What is the life cycle of head lice?

There are three forms of lice, namely the nit, the nymph, and the adult louse.

Nit: Nits are lice eggs. Nits are hard to see and are often confused with dandruff or hair-spray droplets. Nits are found firmly attached to the hair shaft. They are oval, 2-3 mm in length and usually yellow to white in color. Nits take about a week to hatch.

Nymph: The nit hatches into a baby louse called a nymph. It looks like an adult head louse but is smaller. Nymphs mature into adults about seven days after hatching. To live, the nymph must feed on blood.

Adult: The adult louse is about the size of a sesame seed, has six legs, and is tan to grayish-white in color. In people with dark hair, the adult louse looks darker. Females lay nits; they are usually larger than males. Adult lice can live up to 30 days on a person's head. To live, adult lice need to feed on blood. If the louse falls off a person, it dies within two days.

Life cycle: The nits hatch into nymphs, which become full grown lice. In order to produce more nits, the adult lice must mate.

Where are head lice most commonly found?

Head lice are most frequently located on the scalp behind the ears and near the neckline at the back of the neck. Head lice hold on to hair with hook-like claws that are found at the end of each of their six legs. Head lice are rarely found on the body, eyelashes, or eyebrows.

Head lice vs. dandruff

Head lice are often confused with dandruff. Dandruff can easily be distinguished by combing the hair or even just rubbing. Dandruff should be easily removed, but the nits of head lice are firmly attached to the hair shaft.

Reviewed on 1/20/2017
References
REFERENCES:

American Academy of Pediatrics. "Pediculosis Capitis (Head Lice)." Red Book, 30th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2015.

Chosidow, O. "Oral Ivermectin Versus Malathion Lotion for Difficult-to-Treat Head Lice." New England Journal of Medicine 362 Mar. 2010: 896-905.

Devore, C.D., G. Schutze, J. Okamoto, M. Allison, R. Ancona, E. Attisha, and M. Minier. "Head lice." Pediatrics 135.5 (2015): e1355-e1365.

Feldmeier, H. "Treatment of pediculosis capitis: a critical appraisal of the current literature." American Journal of Clinical Dermatology 15.5 (2014): 401-412.

United States. Centers for Disease Control and Prevention. "Head Lice." Dec. 28, 2016. <https://www.cdc.gov/parasites/lice/head/>.

IMAGES:

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4."Male human head louse" by Gilles San Martin

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6."Bugbuster" by Thanks for the polite permission of the Community Hygiene Concern, Joanna Ibarra

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