Health Answers

Why do kids get lice so much more often than adults?

By Courtney Humphries
May 24, 2010

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Q. Why do kids get lice so much more often than adults, and why doesn’t my cat or dog get them?

A. Head lice are parasitic insects that live on the scalp and occasionally in eyebrows and eyelashes. They pose no major health threat but they feed off blood from the scalp, and can cause intense itching and irritation. Sometimes you may notice bumps and redness on the scalp, and small white specks in the hair, which are eggs or “nits.’’ They are most visible in the hair at the nape of the neck and around the ears.

Head lice are extremely common among children, but Dr. Claire McCarthy, medical director of the Martha Eliot Health Center at Children’s Hospital Boston, says, “Head lice have no particular preference for kids — they are perfectly happy on any head.’’ Generally, children are less protective of their personal space, more likely to come into physical contact with one another, and more likely to share personal items like clothing or hairbrushes, which make it easy for the bugs to travel from person to person.

There are thousands of species of lice, and most infect specific host species. The types of lice that occasionally infect dogs or cats are completely different from those that infect humans. “So there’s no need to treat Fido if the family’s got head lice — and no need to panic if the vet says Fido’s got lice,’’ McCarthy says.

It’s a mistaken belief that kids who get head lice are dirty or unhygienic, says Dr. Lou Ann Bruno-Murtha, medical director of infection prevention at Cambridge Health Alliance. The best preventive measure, she says, is to “stress with kids that they shouldn’t share hats, combs, and brushes.’’ Head lice can be treated with over-the-counter medications; the trick is dealing with the nits, which Bruno-Murtha says cling to hair and must be removed carefully with a fine-toothed comb. The subject’s household items such as bedding, draperies, and stuffed toys must also be de-loused.

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