The Educated Patient: Eliminating Head Lice

Guido R. Zanni, PhD
Published Online: Wednesday, June 11, 2014
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Although very contagious, head lice can be treated and prevented.
What Are Head Lice?
Head lice are wingless insects with 6 claws. Lice move by crawling, and their claws tightly hold onto hair. They are about the size of a sesame seed. They appear grayish white or tan. Lice feed on human blood and live close to the scalp. They live and breed on the hair within a quarter inch from the base of the scalp. It’s estimated that 6 to 12 million children get lice each year. Lice occur mostly in children 5 to 12 years of age. Head lice are more common in girls and those living in crowded conditions.1

Head lice are very contagious. Lice are spread by direct contact with someone who has lice or by sharing their clothing (eg, hats, scarves). Once a person gets lice, female lice attach their eggs firmly to the hair. Females can lay up to 10 eggs a day. Lice eggs are called nits. Nits are extremely small and can be confused with dandruff. Nits hatch in 8 to 9 days. Adult lice live up to 30 days, but if lice fall off the scalp, they live only 1 or 2 days.2,3

How Can I Tell if My Child Has Head Lice?
The major symptom of head lice is intense itching. Other symptoms include a tickling sensation or a sensation that something is moving in the hair. Constantly scratching the itch can result in other problems such as a rash. The rash may lead to an open wound that can become infected. Head lice do not cause infections. Infections occur because bacteria infect the wound.1

You can find lice by following 3 simple steps:
  1. Wet the child’s hair. This makes it easier to see lice and prevents them from scurrying away.
  2. Because head lice are so small, use a bright light and/or a magnifying glass to examine the child’s hair.
  3. Separate sections of the child’s wet hair, slowly combing each section. Pay close attention to the hair behind the ears and near the neck. These areas are more likely to have lice than other areas. Because lice do move, you are more likely to see nits that are firmly attached to the hair.4

Treatment for Head Lice
Head lice can be treated with OTC products containing pyrethrins. Read and follow the instructions carefully (Table 14). Common side effects of topical treatments are skin irritation and the feeling that the scalp is burning or itchy. People allergic to ragweed or chrysanthemums should avoid agents with pyrethrins.5

Two treatments spaced 7 to 9 days apart often get rid of head lice. The second treatment is needed to kill nits that have hatched after the first treatment. Because products may not kill all nits, you should continue to comb for nits for at least 2 weeks after the second treatment. Some lice are resistant to treatment; your doctor can prescribe a cream, lotion, or shampoo that kills resistant lice.6

What Can I Do to Prevent Head Lice?
It’s important to teach your children about head lice and ways to prevent it. Head lice can be prevented by following the guidelines in Table 21,2,6,7.

Where Can I Find More Information?
Useful information on head lice can be accessed at the Centers for Disease Control and Prevention website:

Dr. Zanni is a psychologist and health-system consultant based in Alexandria, Virginia.

1. Gholamnia Shirvani Z, Amin Shokravi F, Ardestani MS. Evaluation of a health
education program for head lice infestation in female primary school students in
Chabahar City, Iran. Arch Iran Med. 2013;16:42-45.
2. Parasites - Lice - Head Lice. Centers for Disease Control and Prevention website. Accessed July 20, 2013.
3. Madke B, Khopkar U. Pediculosis capitis: an update. Indian J Dermatol Venereol
Leprol. 2012;78:429-438.
4. Head lice: diagnosis, treatment, and outcome. American Academy of Dermatology website. Accessed July 20, 2013.
5. Smith CH, Goldman RD. An incurable itch: head lice. Can Fam Physician. 2012;58:839-841.
6. Treating head lice. FDA website. Accessed July 20, 2013.
7. Head lice. Accessed July 20, 2012.

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