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Head Lice

 

Graphic courtesy USCDCHead lice, Pediculus humanus capitas, are small parasitic insects. They live on people's heads (or sometimes their eyebrows or facial hair), and feed on our blood.

Head lice are most commonly encountered among children of pre-school or elementary school-age, but they can infest anyone, or any age, of any race, and of any socioeconomic background. Having head lice is not a sign of being "dirty." Anyone can get head lice.

Head lice are most commonly spread from an infested person to a non-infested person by close physical contact or by sharing of hats and other clothing. They cannot jump, hop, or fly from one person to another.

Head lice can, however, crawl from an infested person's head to another person's head. This is a common way that they spread between children in schools and daycare centers when children hug, play, and roughhouse with each other. Fleas also may fall or crawl from a person's head and fall onto furnishings or carpeting, and wait there for another head to infest.

Life Cycle of Head Lice

Head lice begin their lives as eggs, often called nits, that are attached to individual hairs, very close to the scalp, using a strong cement that the mother secretes. Adult female head lice can lay as many as eight eggs per day.

The nits hatch in about a week, beginning a rapid period of gradual metamorphosis. During this period, immature lice may crawl or fall from one head to another, but typically they don't migrate far from where they were born.

It's a myth that lice "look for another head" to infest. They're not migratory insects. If they happen to fall or crawl from one head to another, it's simply by chance. They don't "look for" other people to infest unless they've already fallen off someone's head, in which case they simply crawl onto the next head that they happen to come across.

Lice reach maturity in as little as 10 days, and usually live for a month or so as adults. An adult female head louse can lay eight or so eggs a day, or as many as 250 in her lifetime; so if untreated, a head lice infestation can grow very rapidly.

Head Lice and Human Health

Photo courtesy USCDCHaving head lice can be very emotionally distressing, especially to children, who may be shunned or subjected to cruel teasing by other children if their condition is discovered. When dealing with children (and others) who have head lice, sensitivity and kindness are important.

Also, head lice do not seem to spread any serious human diseases. But they do cause localized itching and swelling, which can lead to infections when the afflicted person scratches the irritated areas and breaks the skin. Some people also may experience localized allergic reactions to head louse bites.

Please note that although head lice have not been shown to transmit serious diseases, the same cannot be said of body lice, Pediculus Humanus corporis, which are important vectors of typhus.

Detection of Head Lice

Photo courtesy of Barb Ogg, University of Nebraska Cooperative Extension in Lancaster County.Very often, parents become aware that their children have head lice when informed by a school nurse. Other signs include scratching, soreness, or irritation of the scalp.

When a person is suspected of having head lice, they should be thoroughly examined for lice or nits. Using the fingertips, gently and methodically spread the hairs apart and look for the insects themselves, bite marks on the scalp, or nits attached to the hairs. Pay special attention to the areas near the back of the neck and around the ears.

Nits are usually attached very close to the scalp; but since hair grows, you may find nit "shells" farther out along the hairs. Nits may sometimes be mistaken for dandruff, but unlike dandruff, nits are attached to individual hairs and don't easily shake off.

(Photo courtesy of Barb Ogg, University of Nebraska Cooperative Extension in Lancaster County. You can visit their excellent head lice site here.)

Next: How to Treat Head Lice