Life Cycle of Headlice

Head lice are commonly spread in areas where children congregate, such as elementary schools, sleepover parties and sports clubs. Understanding the life cycle of head lice can help you treat outbreaks and prevent transmission.

Nits

• Nits are the first stage of lice development. Nits are tiny egg sacs deposited very close to the scalp, firmly cemented to the hair shaft with a glue-like substance. Nits take about 10 days to hatch.

Nymphs

• A newly hatched louse is called a nymph. This second stage in the life cycle lasts from about day 11 to day 22. Nymphs are difficult to spot--although they look like adult lice, they are much smaller. Nymphs cannot reproduce.

Adults

• The louse reaches maturity around day 23. Female lice can lay up to 10 eggs a day until death around day 50.

Checking for Lice

• Regular head checks are recommended for all children when school begins, and especially if an outbreak has been identified. Use a bright light to examine the head at different angles, keeping in mind that eggs range in color from almost transparent to yellowish-brown. If you can't tell whether you've found an egg, try to remove it--if it is difficult to dislodge, it is likely a nit. Pay particular attention to the hairline and behind the ears, and don't forget to look throughout the hair for adult lice.

Treatment

• The first application of lice treatment should be immediately followed by combing for nits. Since any nits you miss will hatch about 10 days later, a second treatment is recommended at that time.