Understanding Head Lice
Guido R. Zanni, PhD
Although very contagious, head lice can be treated and prevented.
Head lice are insects with 6 claws and no wings. Lice cannot hop or fly. Lice move by crawling. Their claws hold tightly onto hair. They are gray-white or tan and the size of sesame seeds. Lice feed on human blood 4 or 5 times a day. Lice live and breed within a quarter inch of the hair from the base of the scalp, especially near the ears and neck. Head lice may also thrive in eyebrows and beards. Lice are most active at night.1,2
Head lice are very contagious. Lice are spread by direct contact with someone who is infested or by sharing clothing (eg, hats) with someone who has lice. Female lice attach their eggs firmly to hair. Lice eggs are called nits, which are usually yellow to white. Nits are extremely small and can be confused with dandruff. Nits hatch in 8 or 9 days. They reach adult size in 9 to 12 days after hatching.2 Lice live up to 30 days. Females can lay 50 to 150 eggs in their lifetime.1,3 If lice fall off the scalp, they die within 2 days.
Six to 12 million children, mostly between 3 and 12 years of age, get lice each year.1,4 It is more common in girls and in individuals living in crowded conditions. 5 Head lice is less common in African Americans.2
How Can I Tell if My Child Has Head Lice?
The first symptom of head lice is intense itching. Other symptoms include a tickling sensation or a feeling that something is moving in the hair. Small red bumps on the scalp or neck may also be present (Table 12).6 Constant scratching can result in open wounds and infections.5
Myths and Facts
Myth: Pets spread head lice.
Fact: Lice cannot live on pet fur.
Myth: Head lice carry diseases.
Fact: Lice do not carry other diseases.
Myth: Head lice thrive in dirty households.
Fact: The cleanliness of a person or house has no role in spreading head lice.
Myth: Insect sprays kill lice.
Fact: Insect sprays should never be used. They may contain harmful chemicals.
Myth: Swimming spreads lice.
Fact: Lice tightly hold onto hair when underwater. Chlorine in pool water cannot kill lice.2
Head lice are treated with OTC products containing pyrethrins. Rid and Nix are brand names of products containing pyrethrins (Table 21,2,7,4). Common side effects of pyrethrins are skin irritation and the feeling that the scalp is burning and itchy. People allergic to ragweed or chrysanthemums should avoid pyrethrins.3
Two treatments spaced 7 to 9 days apart usually get rid of lice. The second treatment is needed to kill nits that have hatched after the first treatment. Because products may not kill all the nits, you should continue to comb for nits for at least 2 weeks following the second treatment. Some lice are resistant to treatment. Your doctor can prescribe a cream, lotion, or shampoo that kills resistant lice.8 There is some evidence that tea tree oil and lavender oil are effective against lice.9 While the American Medical Association recommends tea tree oil, the National Institutes of Health does not recommend herbal treatments. 6,10
If you want to avoid medications, the following methods are recommended for treating head lice.
Apply an oil (eg, cooking oil) or petroleum jelly to wet hair. Using a lice comb, remove nits and lice. Comb the hair for 30 minutes every 2 or 3 days for a 2-week period.3
Remove all hair by shaving the entire head and neck. Lice die if they cannot attach to hair.
Teach your children about head lice and ways to prevent it (Table 32,4-6,8).
The Centers for Disease Control and Prevention has easy-tounderstand information on head lice at www.cdc.gov/parasites/lice/ head.
Dr. Zanni is a psychologist and health-system consultant based in Alexandria, Virginia.
- Madke B, Khopkar U. Pediculosis capitis: an update. Indian J Dermatol Venereol Leprol. 2012;78:429-438.
- Parasites-lice-head lice. Centers for Disease Control and Prevention website. www.cdc.gov/parasites/lice/head. Accessed June 15, 2014.
- Smith CH, Goldman RD. An incurable itch: head lice. Can Fam Physician. 2012;58:839-841.
- Head lice. FamilyDoctor.org website. http://familydoctor.org/familydoctor/en/diseases-conditions/head-lice.printerview.all.html. Accessed June 18, 2014.
- 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.
- Goodman DM, Burke AE, Livingston EH. JAMA patient page: head lice. JAMA. 2013;309:2398.
- Head lice: diagnosis, treatment, and outcome. American Academy of Dermatology website. www.aad.org/dermatology-a-to-z/diseases-and-treatments/e---h/head-lice/diagnosis-treatment. Accessed July 20, 2013.
- Treating head lice. FDA Consumer Health Information website. www.fda.gov/forconsumers/consumerupdates/ucm171730.htm . Accessed June 16, 2014.
- Barker SC, Altman PM. A randomised, assessor blind, parallel group comparative efficacy trial of three products for the treatment of head lice in children: melaleuca oil and lavender oil, pyrethrins and piperonyl butoxide, and a “suffocation” product. BMC Dermatol. 2010;10:6.
- Tea three oil. MedlinePlus, National Library of Medicine website. www.nlm.nih.gov/medlineplus/druginfo/natural/113.html. Accessed June 15, 2014.