What Are Lice?

Lice are small, yellowish gray, wingless insects that live on the body and feed on human blood. There are three species: head lice, pubic lice (crabs) and body lice.

Head lice live on and suck blood from the scalp, leaving red spots that may itch severely. Constant scratching may lead to a secondary skin infection. The females lay small, pale, football-shaped eggs (nits) on the hair shafts close to the scalp. These eggs hatch within seven days and then usually live for several weeks. Head lice are spread through direct contact with an infested person.

Hair Image - Masterfile

Body lice live in and lay their eggs on clothing and go to the body only when they need to feed. They may transmit typhus or relapsing fever (both infectious diseases characterized by a rash and fever), although this is quite rare. Body lice usually affect people who do not change their clothes often enough.

Pubic lice live in pubic hair and are usually transmitted during sexual contact. Less commonly, they may infest eyelashes, beards, armpit hair and hair around the anus.

In general, people at greatest risk for lice infestation are children aged 3 to 11 and those who live in nursing homes or in other crowded or unsanitary conditions. Although lice are terribly annoying and spread quite easily, they are fairly easy to treat and rarely pose a serious health risk. Unfortunately, some head lice have become resistant to currently available over-the-counter treatments.

What Causes Lice?

Lice are not caused by poor hygiene. They are spread by direct contact with a person who has lice. Lice only feed on human blood—you cannot get them from pets. Lice only move by crawling—they do not jump or fly.

  • Overcrowded living conditions increase risk (close contact).
  • Children who attend daycare or preschool and play closely together may spread lice more easily.
  • School-aged children are often affected because of their close daily contact with schoolmates and the use of classroom closets.
  • Head lice can be transmitted through use of an infested hairbrush, comb, hat or set of headphones.
  • Pubic lice are most often transmitted through sexual contact with an infected partner, but may also be transmitted through contact with infested bedding.

Symptoms of Lice

  • Intense itching, usually in hair-covered areas
  • Redness and flaking of the skin
  • Tiny red bite marks
  • Visible lice on clothing
  • Visible nits (eggs) on hair shafts (firmly attached and difficult to remove)

Prevention

  • Teach children to avoid head-to-head contact with others.
  • Check your children periodically for head lice and nits, especially during peak season (August through November and January).
  • Do not wear the same clothes for more than a day or two. Launder clothes often.
  • Bathe or shower regularly.
  • Do not share pillows, combs, hairbrushes, hats or other headwear with others.

Diagnosis of Lice

  • Diagnosis is usually based on self-examination. Lice and their eggs, although small, are visible on hair shafts, skin and clothes.
  • Use a magnifying glass and bright light to spot nits easier.
  • Part the hair in several areas.
  • Use your fingernail to distinguish dandruff from nits—dandruff will come off easily and nits will stay attached to the hair shaft.

How to Treat Lice

  • Several over-the-counter (OTC) and prescription lotions and shampoos are available to treat lice. These products should be applied to all infected areas of the body (follow label instructions) and washed off. Then, using a fine-tooth comb, remove any dead lice or nits from the hair shafts. One or two more applications of the lotion may be necessary.
  • Antibiotics such as Co-trimoxazole (sulfamethoxazole and trimethoprim) is sometimes prescribed as a second line treatment for head lice.
  • Several shampoos are available for the treatment of head lice. Repeated use of these over several weeks is usually required.
  • Combs and hairbrushes should be washed in very hot soapy water to kill any attached eggs.
  • Infested clothing should be washed in very hot water and dried on a high heat cycle for at least 20 minutes.
  • Items like towels, bedding, rugs, upholstery, mattresses and children’s stuffed toys should be thoroughly cleaned (or burned if necessary) to avoid reinfestation.

When to Call a Doctor

  • Call a doctor if symptoms persist despite self-treatment measures.
  • Approved prescription medications include Ulesfia, Natroba, and Sklice.

Sources:

Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference

Simeon Margolis, M.D., Ph.D., Medical Editor

Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

U.S. Food and Drug Administration (FDA)

Centers for Disease Control and Prevention (CDC)

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at Healthcommunities.com

Published: 30 Aug 2011

Last Modified: 08 Jan 2015