The Life Cycle Of Head Lice

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There are 3 different stages in the life of head lice:
-    head lice eggs, also called nits
-    nymphs
-    adult head lice

The life cycle of head lice means the period of time between the moment head lice eggs are laid by the female until the moment head lice die. The head lice life cycle lasts about 45 days.

Head lice reproduce very quickly. The male is a tireless lover who can fertilize 18 females in a row without having a rest. The females mate several times during their adult life, which can vary from ten to forty days, usually about 20 days. They lay up to 10 lice eggs or nits daily.

1. From Egg To Nymph: One Week

Head lice incubation period lasts about a week (from 6 to 9 days exactly), which means that head lice eggs or nits hatch occurs about a week after eggs have been laid. Head lice eggs hatch to release a nymph. The latter resembles the adult lice, but of course it is smaller, and it measures about 1 millimeter, the size of a pinhead

2. From Nymph To Adult Louse: Another Week

The adult stage is reached after approximately 7 days after three successive molts. Thus, from the laying of the egg to the emergence of adults are 17 days, and the adult will live for about 30-40 days.

3. Adult Stage: One Month

The lifespan of head lice when adults is about 30 days. This means that head lice, once they have reached the adult stage, will live for about one month. Actually, they can only live about this period of time on a human host, as they need to feed on blood several times every day. Away from a human scalp, they will die within 48 hours.


Eggs: Nits are laid by the adult female and are cemented at the base of the hair shaft nearest the cycle_1
Nymphs: The egg hatches to release a nymph. life cycle_2
Nymphs mature after three molts life cycle_3, life cycle_4.
Adults: The adult louse is tan to grayish-white life cycle_5. In persons with dark hair, the adult louse will appear darker. Females are usually larger than males.

Frequently Asked Questions – Head Lice Life Cycle

  • How long do head lice live?

On a human head, head lice live up to 30 days.

  • How long does head lice live without a host?

Away from someone’s head (on furniture, carpets, clothing, bedding, etc) head lice can live up to 2 days. This is true for nymphs and adult lice. However, nits can live up to 9 days away from a host (until they hatch).

  • How long can head lice live in clothing?

Head lice can live up to 48 hours in clothing. After this time, they die because they cannot feed on human blood. As far as nits are concerned, they can live up to 9 days on a hair away from a head.

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{ 2 comments… read them below or add one }

Laura November 3, 2011

I read you can tell how long the infestation is by how far down the hair shaft the nit is. We found 9 lice and 16 nits on my daughter and have not found anymore since. Some nits were right at her head and most maybe an inch away from her head. We did not find any hatched nits as we found the lice cleaning out flour from her hair from halloween so it was hard to tell what was what and it took a couple days to wash out the flour!

Rochelle April 9, 2012

I found the lice on my daughter because I noticed her scratching her head a lot. When I saw the louse on some hairs, I pinched it between my fingers and slid it down the hair shaft to get it off. At first it looked like a wing from a gnat or something, it was so small! I went out immediately and bought lice shampoo. I only “saw” 3 lice ; the one I described previously, one while putting on the lice shampo, and one while combing through her hair with the nit comb. I found a few hundred nits…I didn’t count, but there weren’t so many that I couldn’t have. It was a long and uncomfortable process, and I’m very glad we did it. I checked her head again the next day and found some nits I missed. I’m going to keep checking daily, and I’ll reapply the shampoo on what will be the 9th day after the first application. I’ve vacuumed my furniture and car as well. Washed and dried all the bedding in HOT. Most importantly … I told everyone of our friends who she may have had head to head contact or who came for a sleepover before we discovered the lice.

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