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Created on 
October 27, 2022
Updated on 

The amount of effort required for successful lice treatment can be greatly minimized when you understand the life cycle of lice, leveraging that knowledge based on peer-reviewed studies to attack lice when they are most vulnerable. There are three stages of the head lice life cycle. While all stages of lice need to be addressed, timing lice treatment at a time when lice are vulnerable but unable to multiply will greatly increase your chances for success.


The average louse, from the time they are laid until they die naturally on the human head, lives for approximately 30 days. For the duration of their natural lives, lice stay on the human head. Lice will not reproduce until they enter their adult stage. They will continue to multiply exponentially until they are treated. Head lice will not go away on their own.


As mentioned, there are three stages to the life cycle of head lice, beginning with the lice eggs which are about the size of a sesame seed and are laid on the strands of human hair. After lice eggs hatch, they are baby bugs called nymphs. During this time, they spend their time, at first, just feeding on the human blood from the human scalp. Once they mature into adult lice, they produce eggs of their own. Day by day, lice progress as follows:

  • Day 1 - the nit is laid, growing, and becoming more visible.
  • Day 7 - the eggs hatch - this is the nymph stage.
  • Day 15 - Nymphs have now matured and entered the adult stage. Female lice and male adult lice are now able to reproduce.


life cycle of lice

The main stages of head lice are the egg, nymph, and adult louse. All stages of an infestation need to be addressed to get rid of head lice. A case of head lice can be easily confirmed after a few strokes through the hair with a comb designed to remove nits.

Eggs (Nits)

Head lice eggs, called nits, are laid on the individual strands of hair, close to the hair shaft. If you are trying to find head lice in your child's hair or on another person's head, you should thoroughly look through the whole head. The eggs blend in with the hair and are about the size of a sesame seed. They are easier to spot because they are firmly attached to the hair strand of their human host. Once laid, a louse egg remains attached to the hair strand. You will find them within 1/4 of an inch of the scalp, near the base of the hair shaft where it is the optimal temperature. Nits will hatch after about 7 days. During this time they are protected by the shell of the egg from any attempt at treating lice, whether with medicated shampoos or over-the-counter pesticide treatments. Lice eggs can be removed with a good nit comb.


After head lice eggs are hatched, an individual head louse will begin the 2nd stage of its life, the nymph stage where lice removal is ideal. Now a bug with six legs and appearing grayish-white in color, nymphs mature over the course of the next 7 days where they will undergo three moltings. The first molt will be on day 8, one day after they hatch, the second molt on or around days 10 and 11, and the third molt on or around day 12. During this time, the nymph will prefer to remain close to the scalp where it is warm, feeding off of the human host. Because of the bites and now mobile bugs, you may begin to notice repeated scratching from an irritated scalp. While lice do not spread disease, it is at this stage that a person can spread lice, thus making them contagious. Lice spread by way of head-to-head contact. Anyone having been in close personal contact with someone that has lice can contract head lice.


After two weeks, a head louse will have completed the nit phase and nymph phase (first molt, second molt, and third molt) and will enter the final stage of its life. Now an adult louse, a bug will begin the most active part of its life. It is at this stage that an infestation will begin to multiply and become increasingly contagious. During the course of the next two weeks or a little more, adult lice, both female lice and male lice, will feed off of the human scalp and begin to reproduce. A single female louse can lay close to 100 eggs. A person with what is now a full-blown infestation consisting of lice and nits will be able to infect anyone they are in close contact with as head lice spread mainly via head-to-head contact.


head lice life cycle

In an effort to treat lice thoroughly, those who don't know what lice look like and are unsure about where lice come from may set off doing unnecessary tasks around the home, like cleaning bed linens in hot water and putting stuffed animals in sealed plastic bag for an extended period of time. This is unnecessary as the only host for human head lice, pediculus humanus capitis is the human head. Head lice live on the head, not in the home. Once separated from its host, a louse will die after 24-36 hours. Therefore, treating lice, including lice removal of all lice and nits from the head will effectively get rid of lice.


Lice eggs are firmly attached to the hair. Once laid, they do not move from the hair. However, if a person naturally sheds a strand of hair with an egg attached to it, it will not re-attach to another person's head. Hypothetically, if an egg hatches shortly after it is separated from the head, away from the warmth and its food supply, it will die soon after emerging from the protective shell of the egg.


When dealing with head lice, it is important to remember that they live on the head, not in the home or on other objects. Many people have been told that they should clean everything, vacuuming, laundering, and sanitizing surfaces in the house to make sure a lice infestation is gone. However, if you properly treat the head, any head lice present on other objects like hair accessories, hair brushes, bedding, scarves, shirts, etc., will eventually die on their own within about a day. You must kill all of the adult lice, as well as the nymphs, and extract the eggs to end a lice infestation. As for disease control on objects that head lice may have been in contact with, pediculosis does not cause disease so no additional action is necessary.


No matter what phase of their life your infestation has progressed to, nit, nymph or adult louse, head lice can be eradicated. Depending on what stage your infestation is, it may prove to be very time-consuming for you to address it on your own. Just one head louse left behind can trigger a whole new infestation. Most families do not have the time or the patience to complete the entire process of lice treatment, so choose to contact professionals. LiceDoctors can treat any case of head lice, even those with health conditions or risk factors that may exclude them from other treatment options. Book an appointment with a local technician that will get rid of lice and educate you on preventive measures to ensure the lice are gone for good!

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