If you’re like most parents, you may have found that hair lice treatment is an iffy thing. After all the work you’ve done to get rid of them, they just seem to pop up again in a week or so. To get rid of lice for good, it’s important to understand the head lice life cycle.

Biology 101

Here’s where you’re going to learn more about these bugs than you ever wanted to know. But remember that a little knowledge goes a long way when dealing with the pesky things.

The cycle starts when your child is exposed to someone who is already infested with these parasites. They’re spread only by direct contact, either with an infected head, or by borrowing a hat, comb, hair tie, or towel used by someone who already has them.

Once a female louse is on the head, she can start laying eggs, which are called nits. These nits are extremely small. They’re found close to the scalp, where warm conditions are perfect for them.

One female can lay three to five eggs a day for seven to ten days. This means she’ll produce anywhere from 20 to 50 eggs over the course of her life.

A tea tree oil shampoo, using plenty of hot water, will kill most adult lice, which is why it’s easy to think you’ve gotten rid of them. The problem is the nits. They’re covered with a sticky goo that glues them to the hair shaft. If you don’t remove the nits with a fine-toothed comb, they hatch out into nymphs, or baby head lice, in another seven days or so.

Nymphs are hungry little critters. They need a human blood meal within minute of hatching, or they’re history. And of course, they’re easily removed by another hot shampoo treatment at this point. If they survive, they mature in seven to ten days, when the young females start laying eggs, starting the cycle all over again.

How Long Can Hair Lice Live?

From nit to egg-laying adult takes about 15 to 20 days. Add in another week or so of egg-laying and you’ll find the average louse only lasts for a little less than a month. That’s a short lifespan for something that causes so much aggravation.

Now you can understand why hair lice treatment doesn’t always seem to work. It’s important to get those nits out of your child’s hair to prevent a repeat show in another week. A second treatment at the seven-day mark is essential, too. It only takes a couple of lice to start the cycle all over again.