Lice life cycle: everything we need to know 2026

Lice are very common in children, especially when they go to daycare or school, where contagion is much easier. In fact, these stubborn bugs can not only be quite contagious, but they can even be difficult to remove from your hair. And although there are times when the infestation is more common, they can be present at any time of the year. It is enough for one child to have them for them to be easily transmitted to the rest of the children.

There are a series of symptoms that can help you know if a child has lice or not. Since it is detected in plain sight in the hair, it is accompanied by a tingling or tickling sensation on the scalp, which can also become very uncomfortable itching.

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Since they are parasitic insects, they need the presence of a host that provides them with food to live. In this case, they feed on the blood they obtain from the scalp, which is why they live near it (although it is also possible that, occasionally, we can find them on the eyebrows or eyelashes).

They are extremely common, with an estimated 6 to 12 million people contracting them each year. Of them, the majority are children between 3 and 11 years old. And, indeed, a common cause that causes lice to be much more common among the little ones in the house is found in the fact that, at this age, they are usually in close contact when they play.

Do you know how contagion occurs?

Before inquiring about the life cycle of the lice, it is necessary to know how contagion occurs. And although you may think otherwise, the reality is that lice do not have the ability to fly or jump (as happens, for example, with fleas). That is, they cannot jump from one head to the other.

On the contrary, contagion can occur through direct contact between someone who has them and a person who does not. But indirect transmission or contact can also occur, either through a scarf, cap, hat, comb or brush.

What is the life cycle of a louse like?

The life cycle of a louse begins from the precise moment it hatches into an egg, also known as a nit. The nit is approximately 1 millimeter in length, and usually has a whitish yellow appearance.

It has the ability to firmly adhere to a strand of hair near the scalp.

After approximately 7 to 10 days, the nit hatches and becomes what is known as a nymph (also called a young louse). In general, they are between 1.1 to 1.3 millimeters in length, and their color is white or tan. They will then take between 9 to 12 days to mature, thus becoming adult lice.

Adult lice, when mature, are usually no larger than 2 millimeters in length, have a characteristic black or dark color, and females are usually larger than males. When mature, they live approximately 3 to 4 weeks.

How long can a louse stay on the scalp?

Immediately after the nit has hatched, the nymphs need food to survive. With the help of their claws, they begin to crawl from the strands of hair to the scalp, and begin to feed on the host's blood (also doing so several times a day).

As long as there is a food source available (for example, blood from the scalp), an adult louse can live up to 30 days. And, in the meantime, they can continue to multiply. In fact, a female louse can lay up to 6 eggs per day.

And how long can they live off the scalp or without food?

Outside of the scalp, or the human body itself, adult lice cannot live beyond 24 hours. Although if you have identified the presence of lice at home, it is best to isolate and wash those areas - and also your clothes - within at least the next 72 hours.

In the case of nits, however, they cannot live without the existence of a human host, since they need the heat of the scalp for incubation before hatching. And, as soon as they are born, they need food, which they obtain, as we have already told you, from human blood. Therefore, nits that come off the hair may end up dying before they hatch.