Head Lice (Pediculosis Capitis)

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Images of Pediculosis Capitis (Head Lice)


Pediculosis capitis is another term for infestation with head lice, a highly contagious disease that often occurs in schools. It can also cause outbreaks anywhere that people live in close quarters. Intense itching of the scalp is the most prominent symptom of a head lice infestation.

Lice are very small insects that feed on human blood. In head lice, the female louse attaches her eggs (nits) to the base of hair shafts. The nits then hatch 8–10 days later. While the adult louse cannot survive more than 2 days off of the human head, a nit can stay alive for up to a month off the body (eg, on clothes, hairbrushes, or carpets), which is what contributes to how contagious they are. Lice can spread from person to person by close personal contact and by sharing belongings.

Who's at risk?

Head lice are seen in all populations and ages, although they are less common in black individuals and in males. Head lice tend to be more common in the summer months and in warmer climates.

Signs and Symptoms

The most common locations for head lice infestations include:

  • Scalp, especially the hairline near the neck
  • Behind the ears
  • Neck

Moving lice or non-moving nits may be seen on the scalp and hair. Each louse is approximately 1–2 mm long and is white-gray in color. The white nits are smaller (0.5 mm), are firmly attached to the hair shaft, and are usually located very close to the scalp. In longer-standing infestations, the nits may be farther away from the scalp. In addition, small, red bumps may be seen on the scalp, neck, and shoulders. If scratched aggressively, these bumps may become scabbed.

Self-Care Guidelines

The following self-care measures may be helpful if you think you have head lice:

  • Search for lice and nits on wet hair using a fine-toothed comb (louse comb). Examine the scalp in strong light, using a magnifying glass if necessary.
  • Use an over-the-counter medication for head lice exactly as directed. These medicines are insecticides and should not be applied in greater quantity or more frequently than recommended. These medications are not recommended for children younger than 2 years old.
  • Wash household items such as bed linens, towels, and hats in hot water, and dry them using the hot cycle for at least 20 minutes.
  • Wash any object that the infected child has come into contact with in the past 48 hours in hot water for at least 5 minutes.
  • Seal potentially contaminated but non-washable objects in plastic bags for 2 weeks. (The lice will die within 2 days, and the nits will hatch and die within 2 weeks.)
  • Vacuum floors and furniture used.
  • Do not share combs, hair brushes, hats, towels, bedding, clothing, headphones, stuffed toys, or other personal items with someone who has head lice.

When to Seek Medical Care

See your doctor if self-care measures have not successfully killed off (eradicated) the lice infestation. Also call the doctor if you see any signs of bacterial infection, such as redness, swelling, pain, or pus, particularly in areas where you may have been scratching the skin. Additionally, call the doctor before using any louse medicines if you are pregnant.

Treatments Your Physician May Prescribe

In order to make a diagnosis of head lice, the doctor must see a louse or a nit on the scalp. Occasionally, a Wood's lamp is used to look for lice and nits. In this procedure, the doctor shines a black light at the scalp, and the insects and eggs appear as yellow-green fluorescent spots under this light.

Once the diagnosis of head lice has been confirmed, the doctor may recommend one or more of the following treatments in addition to the self-care measures outlined above:

  • Permethrin lotion or shampoo
  • Malathion lotion
  • Lindane lotion, cream, or shampoo (not used as much anymore due to potential toxicity)
  • Ivermectin pills

Trusted Links

Clinical Information and Differential Diagnosis of Pediculosis Capitis (Head Lice)


Bolognia, Jean L., ed. Dermatology, pp.1324-1326. New York: Mosby, 2003.