What are head lice? Louse, nits and transmission

You too have probably been confronted with the topic of head lice at some point. Regardless of whether your child was infested with the small animals itself or was warned of a lice infestation in your kindergarten or at school, at some point every parent has certainly had to deal with the prevention or treatment of a lice infestation . But what exactly do lice do on the head and what do they look like?

Characteristics of head lice

Head lice are the most common type of lice in Germany and Europe. In addition to her, there are also the clothes louse and the pubic louse, which can infest humans. However, these have become very rare in our latitudes. In the case of a lice plague, it is actually always about the head lice.

Head lice are parasites with six legs, mouthparts, and a proboscis that they use to suck blood from the human scalp. An adult louse has a flat body about 2 to 4 millimeters long, about the size of a sesame seed. The color of the lice is gray to transparent, immediately after sucking blood they are slightly darker, brownish or reddish in color. Head lice cannot jump or fly, but they can move very quickly in human hair by crawling. They have grappling hooks on their feet, which they use to hold onto their hair particularly well, allowing them to cover a distance of up to 30 centimeters in 60 seconds. The texture of the hair is irrelevant, the louse feels equally comfortable in long, short, light, dark, curly or straight hair.

Head lice feed exclusively on human blood, which they have to suck from the scalp about every four hours to survive. To do this, the louse pricks the scalp with its suction proboscis like a fine needle. Although head lice, which are present at all times of the year, do not transmit disease in Europe, their body waste and saliva, which keeps the blood fluid during sucking, causes an unpleasant itching, similar to that of mosquitoes. If the louse can no longer drink blood, it dries out relatively quickly and dies after 55 hours at the latest. It is therefore usually not necessary to specially clean the apartment after a lice infestation .

Reproduction and life cycle of head lice

The life cycle of the louse on your child’s head begins with the louse itself, as eggs cannot be transmitted. Since only adult females can lay eggs, one must get onto your child’s head from another head so that it can reproduce there. A female lice can lay up to ten eggs a day, which are attached to the hair with a water-insoluble glue in close proximity to the scalp. The louse can develop best at a temperature of around 30°C, whereas the development of the larva in the egg cannot take place at a temperature below 24°C. Head lice find the ideal temperature for their eggs on the temples, on the back of the neck and behind the ears, which is why the concentration of lice eggs is usually highest in these areas.

What is a nit?

The eggs of the louse are protected from external influences by a solid chitinous covering, the so-called nit. The nit has a kind of lid with breathing holes so that enough oxygen can get through to the larvae. It represents an approximately 1 millimeter thick, brownish thickening in your child’s hair and can easily be mistaken for normal hair dandruff. In contrast to dandruff, however, it cannot simply be brushed off or brushed out, but rather adheres firmly to the hair. Since the naked eye cannot tell whether a nit contains a live egg or not, the term is used synonymously with the actual egg.

From larva to louse

The larvae hatch six to ten days after the eggs are laid. With a diameter of about one millimeter, they are significantly smaller than adult lice and therefore more difficult to detect. They are also largely transparent and look a bit like small crumbs or grains of sand. Since the larvae of the louse have not yet fully developed their clenching legs, they always remain close to the scalp during their first week of life and do not leave the host. There is no risk of infection from them. Within 10 days to 3 weeks, the larva molts three times and develops into a sexually mature louse. After mating, it takes about two to three days until the female lays eggs and the cycle from egg to larva to louse begins again.

Adult head lice have a lifespan of a few weeks, with males living two to three weeks and females around four weeks. During this time, the louse can lay up to 300 eggs to maintain its species and cause a sizeable infestation in a human.

How can head lice be transmitted?

First of all, it is very important to note that head lice are not, as is often wrongly assumed, a sign of poor personal hygiene. Lice feed exclusively on blood and not on dirt or skin cells on the scalp. In fact, head lice even prefer freshly washed hair, as greasy hair makes it harder for lice to attach their eggs. All people can be affected by lice, regardless of their origin or social class. A lice infestation is nothing to be ashamed of!

Head lice are almost exclusively transmitted from person to person. When two people’s hair comes into contact, the lice use this connection as a bridge to quickly crawl onto the new host’s head and spread further. Pets pose no danger as carriers.

It is extremely rare for head lice to be transmitted through objects. Since the louse dies fairly quickly without its regular blood meal, it will not leave a host’s head voluntarily. Occasionally, a louse may become lodged in headgear such as a hat or bicycle helmet that is used by different people within a short space of time. Transmission through a comb or brush with a louse caught between the tines is also conceivable. However, transmission via objects is generally rather unlikely.

In our special “Head lice” you will find more useful tips on the subject.