You're not immune to head lice just because you're older than 11. Anyone can get them-no matter how immaculate your personal hygiene is. But what ARE these creatures, and how can you keep them from infesting your hair? Head lice are tiny, wingless insects that LIVE on, lay EGGS on, and FEED off your scalp. Even though they're only about the size of a strawberry seed, their bites can make your head EXTREMELY itchy. This is because their left-behind saliva can trigger an allergic reaction in most people's skin. The good news... although they might make you scratchy, they AREN'T harmful and DON'T carry disease. Still, they're probably something you want to avoid. One way to avoid lice is to steer clear of other people's things. This includes sharing hats, headphones, brushes, hair elastics, and even clothing-especially if a person is infected. The EASIEST way lice can crawl, though, is from one person to another through close contact. They're so common in children because kids are CONSTANTLY playing near each other. If you're unlucky enough to bring home a family of lice, there are fairly INEXPENSIVE ways to get rid of them. You can kill them off with shampoos, lotions, and other topical medications found in almost any drugstore. Look for ones containing 1 percent permeterin or pyrethrin. Remove dead lice and their eggs--known as NITS--out of your hair with a fine tooth comb. Keep a close watch on your scalp over the next week. If over-the-counter solutions don't do the trick, your doctor can prescribe something stronger. Malathion, Lindane, or Benzyl alcohol lotions, creams and shampoos can be rubbed into the scalp to take care of critters once and for all. Lice don't survive very long without a food source. So getting rid of them from your house takes a thorough cleaning. Make sure to wash ALL the clothes and bedding you used before treatment in water measuring at least 130 degrees. If it can't be washed, have it dry cleaned or sealed in plastic for two weeks. For more ways to keep your scalp healthy, check out the rest of the videos in this series.