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Last week, we ventured into the world of bedbugs. Rather than frighten you off, this only seemed to when your appetite for episodes on creepy, crawly parasites. You want us to cover lice. I bet some of you are already itching your heads. Too late. Lice are the topic of this week's Healthcare Triage:

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John Green -- Executive Producer
Stan Muller -- Director, Producer
Aaron Carroll -- Writer
Mark Olsen -- Graphics
Last week we entered into the world of bed bugs. Rather than frighten you off, this only seemed to wet your appetite for episodes on creepy, crawly parasites. And now you want us to cover lice. I bet some of you are already itching your heads. Too late! Lice are the topic of this week's Healthcare Triage. 

As a pediatrician, there's little you dread more than seeing on your schedule kids with lice. You may remember the days in school when someone in the class had lice, and then everyone in the class had to have their heads examined closely for the foul louse. Lice are tiny bugs that live in the hair of your head. They feed on human blood a number of times a day, so they like to live right on you. Awesome. About 6-12 million kids a year get infested with lice, and like bed bugs, they don't really spread much disease. They can be tough to see because they can be gray or brown and only about an eighth of an inch long. Grown-up lice lay eggs that are called nits. These nits or eggs may look like lose white dandruff or flakes in someone's hair, but they're actually stuck very tightly to the strands of hair and don't wash off easily. Lice are baby making machines! A female louse, the singular of lice, lives for only about 30 days, but she can lay more than 2,600 eggs in that month! Female lice can actually store sperm inside of themselves, so mating just once can allow them to lay fertilized eggs for their entire lives. 

Lice can definitely spread through direct contact with someone else who has head lice. If your head touches the head of a person with lice, their lice can happily move onto you and set up camp in your hair. That's how most little kids get them. Head lice don't jump or fly. So for a long time people thought this was kind of the only way they could move from one person to another. Lice require human beings in order to stay alive, and many people thought that only the adult lice were strong enough to infect another person. Unfortunately, all of this was wrong. You can also get lice even if you don't come into direct contact with another person's head. You can get lice from sharing a comb, a hat, a headband, or any other hair accessory. You can get lice from baseball hats, headphones, pillows, and even upholstered furniture. Both young lice, called nymphs, and adult lice can live up to three days when they aren't on human beings. Eggs can survive and still hatch into more lice for ten days. Scientists have tested whether lice can transfer from a scenario where a single strand of hair touches a louse that is on a suspended thread of the sort that you would have on an upholstered chair or a pillowcase. And they can. They're ridiculous! Another study examined whether lice can be transferred from pillowcases. And they found that while lice did move onto the pillowcase at night, only a small number of lice did transfer. Depressingly, it's possible for lice to get onto a pillowcase and subsequently infect a new person, but it's a much less common way to get infected than to be in close contact with someone else's head or comb.

Because it's possible, you need to change pillowcases so you don't reinfect yourself or infect someone else. Lice can be killed on pillowcases by washing them in hot water or by 15 minutes in a hot clothes dryer. Lice also seem to have an instinct to move quickly away from light or to move when hairs from which they are living are disturbed. This makes them very quick at finding new places which they can live, even if that new place is farther away from their original head of hair. It can also make it hard to see them when people are looking for them. Studies of lice movement have also found them crawling in the pillows and the towels of people with lice who have just shampooed, washed, or dried their hair. Combing the hair of someone with lice with a normal comb leaves lice on the comb, on ground, and on the clothing of the person who does the combing! Blow-dryers can also send lice flying into the hair where they can land on other people or on fabrics, where they wait around for new people to infect. You can vacuum lice up with a regular vacuum cleaner, but hand vacuums don't pick up all of the lice and nits that can cause more infestations.

Because lice can be so incredibly infectious, it can be really hard to get rid of them, especially once someone in your house has them. Getting infected doesn't mean you're dirty or living in bad conditions. It just means that these wily little buggers made a successful attack on your head. Okay, to get rid of lice your best bet is to use a special shampoo designed to kill them, and then to use a special comb designed to get rid of the sticky nits attached to the hairs. You should consult your doctor about which medication shampoo to use, especially since some aren't very safe for young children or pregnant women. Lice can survive under water for much longer than people, so don't think you can drown them. And chlorine in pools doesn't do much to harm them either. In addition to the rounds of shampooing and combing, you gotta do a lot of cleaning. Because lice can live on things like pillowcases and hats, you should launder everything that the infected person may have come in contact with. This means washing their bed sheets and towels, and vacuuming all the floors, carpets, and upholsteries in the house. Lice are nothing to be ashamed of. And there's no cause to panic. But that doesn't mean you shouldn't be wary, and that you shouldn't and take them seriously. 

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