Health A-Z


Clinical Definition

Lice are blood-sucking parasites, known as Pediculus humanus capitis if on the head; Pthirus pubic if in the pubic area; andPediculus humanus corporis if elsewhere on the body. Infestations are typically the result of close person-to-person contact. Incapable of flying or hopping, the parasitic insects must crawl instead. Treatments with prescription or over-the-counter remedies can quell infestations.

In Our Own Words

Lice are tiny, crawling blood-sucking insects that can affect the head – specifically, the scalp – or other body areas, including the pubic area. Body lice, head lice and pubic lice or crabs differ slightly in appearance, but they are all usually spread by close person-to-person contact. Head lice outbreaks are particularly common in children of school age, who often share combs, towels or hats and who ease transmission of the lice in a variety of ways.

Head lice infect the head and neck, attaching their eggs (called nits) to the base of the hair shaft. Body lice live and lay eggs on clothing and move to the skin to feed. Pubic lice are usually found attached to the pubic hair, but sometimes land in the eyebrows, beard, armpits, mustache or chest. On close exam, the tiny nits of lice are sometimes visible; hatched nymphs and adult lice are also sometimes visible, but they can move and become lost fairly quickly. Dogs, cats and other household pets don’t transmit human lice.

Over-the-counter treatments or prescription treatments usually help manage the problem.

Symptoms and Side Effects

  • Itching
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