Lice: How do I get it?

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 a lot!

— 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're 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. Typically, they spread by direct contact with the hair of someone who already has head lice. 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 US among children ages three to eleven. The good news is that while they may be undesirable, they don’t pose other health risks nor do they spread disease — and an infestation is treatable.   

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 aren't contracted from swimming in communal pools, and pets or other animals don’t 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 can’t 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. However, the difference is that nits and lice won’t flake or fall off the hair and scalp like hair spray residue or dandruff. Knowing these details can help with a visual identification to confirm whether or not a person is experiencing an infestation.

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

List from the Centers for Disease Control and Prevention (CDC).

If you do have head lice, there’s no need to worry — but there may be a need to get nit-picky. Heading over to the nearest pharmacy to pick up over-the-counter (OTC) medications is a good next step. More specifically, treatment includes a non-prescription shampoo that kills the lice, which can then be combed out of hair along with nits using a fine-toothed nit comb (usually sold in lice medicine packages). Some medicated shampoo treatments kill both the lice as well as the nits, but not all. As such, pairing the shampoo with combing is key. If you’re unsure about which treatment to choose, consulting with a health care provider for guidance is recommended (doing this is advised particularly when treating young children). As for any items that may have come into contact with lice, further action may be taken. This includes machine-washing clothes and bedding on a hot water cycle, soaking combs and brushes in hot water, and vacuuming rugs and carpets after diagnosis with a lice infestation is also highly recommended. Items that can't be washed may be either dry-cleaned or sealed in a plastic bag for a period of two weeks.

Lastly, there are some cases in which seeking out medical attention may be warranted. Those who are pregnant are advised to speak with a health care provider before using any medicated shampoo treatments. For those who are able to use the shampoo treatment, it’s possible that the lice will persist after one round of treatment. If this happens, talking with a medical professional about retreatment options is a good next step. Similarly, if any sores from scratching the lice bites become infected, it’s wise to get it checked out. For even more answers to your louse-y questions, the CDC is a great resource.

Last updated Nov 02, 2018
Originally published Jul 19, 2013

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