Dear Alice,

I want to know how you get lice in the first place. Does it just happen when you touch someone else's hair? I know using someone else's hairbrush can put you at risk. But I want to know — where does it come from and how do I get it?

Thanks alot!

— Worried

Dear Worried,

A head louse is…well, a louse-y and very annoying creature! Also known as Pediculus humanus capitis (or lice if you are talking about a whole bunch of ‘em) are parasitic insects that live in hair on the human head. Head lice, which feast on human blood several times a day, travel from one person to another by crawling — they can’t hop or fly. They spread by direct contact with the hair of someone who already has head lice. Lice are not dangerous and do not spread disease.   

There are several common misconceptions about ways to contract lice. For example, personal hygiene and household cleanliness have nothing to do with getting head lice. Head lice are not contracted from swimming in communal pools, and animals do not contribute to their transmission. Lice are able to crawl from one person to another during sporting activities, play or sleep in close quarters, and, rarely, when people share items such as hats, scarves, towels, or bedding. An adult head louse can live about 30 days on a person’s head but will die within one or two days if it falls off a person, as it cannot survive without human blood.

Head lice and their eggs, also called nits, are almost always found on the scalp, particularly around and behind the ears and near the neckline at the back of the head. They are very hard to see: a nit is about the size of a knot in a thread, and an adult head louse is about the size of a sesame seed. They’re often confused with hair spray residue or dandruff.

In the United States, head lice infestations are most common among children in childcare and elementary schools, as well as among the household members of those children. An estimated six to twelve million infestations occur each year in the U.S. among children ages three to eleven.

Common signs and symptoms of a head lice infestation include:

  • Tickling or a feeling of something moving in the hair
  • Itching, caused by an allergic reaction to the bites of the head louse
  • Difficulty sleeping due to irritation (head lice are most active in the dark)
  • Sores on the head caused by scratching

If you experience any of these signs or symptoms, you can make an appointment with your health care provider for a visual inspection of your scalp to determine whether you have lice or not. If you do have head lice, however, there’s no need to worry! Over-the-counter (OTC) medications are available and a health care provider can let you know which one to use. Treatment includes a shampoo that kills the lice, which can then be combed out of hair with a fine-toothed nit comb (usually sold in lice medicine packages). Machine-washing clothes and bedding, soaking combs and brushes in hot water, and vacuuming rugs and carpets after diagnosis with a lice infestation is also highly recommended. It’s possible that the lice will persist after one treatment. If this happens, contacting a health care provider about retreatment options is likely your best bet. For more information about lice, check out the Centers for Disease Control and Prevention (CDC) site.


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