NEW YORK — For a relatively harmless pest, the head louse is greatly feared among parents of young children.

Six to 12 million children age 3 to 11 get lice every year, according to the Centers for Disease Control and Prevention.

While lice are contagious, they aren’t hardy or resilient. Here’s how to deal with an infestation.

HOW DO YOU KNOW IT’S LICE? They can be easy to miss. Adults, grayish white and the size of a sesame seed, are most active at night and hide from light.

Nymphs, the baby lice, look similar but are smaller. Eggs, or nits, are what you usually find in a home check.

The best places to check for eggs are behind ears or at the nape of the neck, where hairs are easier to isolate.

I FOUND NITS. WHAT NOW? Lice are icky but harmless. “They do not carry disease,” said Dr Candace Johnson, an assistant professor of pediatrics and hospital epidemiologist at Columbia University.

First, check everyone. Lice pass through head-to-head contact, which is why kids who pile onto classroom rugs are most susceptible.

Then it’s time for treatment. Over-the-counter products like Nix and Rid that contain permethrin or pyrethrins can kill adult lice.

Lice have a two-week life cycle, so you need to apply products twice, a week or so apart.

WHAT ABOUT COMBING? Creams and shampoos can’t kill eggs, so your child will still have nits in between treatments. Combing is the only way to remove them.

You need a fine-tooth metal comb designed for lice removal. Start with wet hair and go through small sections. Repeat the process every two to three days for two weeks.

Remember to still use medicated cream as directed. Any nits missed during combing can hatch, sending you back to square one.

HOW DO I THOROUGHLY CLEAN MY HOUSE? Wash sheets, towels, hats, clothes and jackets in hot water and dry them on high heat. Remember that adult lice cannot live away from a human head for more than a day or two.

If your child’s stuffed animals can’t go through the washing machine, put them in a plastic bag for two weeks. Make sure to vacuum couches, rugs and car seat headrests

This article originally appeared in The New York Times.