Problems caused by head lice

Head louse: a human blood-sucking parasite

poux 1

The head louse, or Pediculus humanus capitis, is a small insect (2 - 4mm long) that feeds on human blood: the louse bites the scalp, injects its saliva and swallows blood. It only lives on human scalps, which provide it with the optimal humidity, heat and food conditions for surviving and growing.

What are the risks for infested individuals?

poux 3

Head lice do not carry bacteria or pathogenic viruses and they do not transmit diseases.

However, while feeding, the louse injects its saliva, which contains anti-coagulants to stop the blood from clotting, therefore making it possible to drink. The injection of this saliva containing irritating anti-coagulants can cause uncomfortable itching in infested people. When people scratch the bitten areas, bacteria and other contaminating agents under the nails can penetrate into the skin, which sometimes causes skin infections (impetigo).   

A serious public health issue

The infestation can stay relatively mild as long as the sufferer does not scratch himself. Nevertheless, it is considered a significant public health issue due to:

  • The costs incurred by anti-head lice treatments, which can have a substantial impact on the family budget;

  • The toxicity concerns associated with anti-head lice products;

  • The ease with which it is transmitted through densely populated locations (schools, day nurseries, etc.);

  • The persistence of infestations;

  • The stigmatisation provoked by lice infestations; children affected are often snitched on and blamed by their peers or teachers.

Although they do not directly transmit diseases, head lice are the cause of physiological and psychological unpleasantness among those infested. Head lice infestations are difficult and expensive to fight against.

What are head lice?

Head lice reproduce very quickly

poux 2

The life cycle of a head louse lasts an average of 25 days. A female lays an average of 5 eggs (nits) per day and lays them firmly at the root of the hair with a glue-like substance. Newborn lice will leave the nits and hatch after 8 days. Within 15 days, these newborn lice are able to reproduce and start the cycle again.

How do you catch lice?

Head lice do not jump or fly, but powerful pincers at the end of their legs enable them to quickly climb up strands of hair or onto clothing fabric. As such, they are able to move to a new host when head-to-head contact is made or by travelling from one item of clothing to another.

Head lice can survive up to 24 hours without eating and be far from a scalp, which is why the personal possessions of those infested, such as hairbrushes, combs, hats, pillowcases, etc. can also be sources of new infestations.

Who can suffer from a pediculosis (lice infestation)? 

poux 4

Pediculosis is an infestation of an organism by lice and can affect all human beings, regardless of age, sex and personal hygiene. However, school-age children are the most affected age group, with an estimated incidence rate between 2 to 15%. At school, daytime nurseries and holiday camps, children frequently come into direct contact with each other. In addition, their clothes are often piled up or hung up next to each other, which facilitates the migration of lice from one child to the next.

Head lice are parasites that exclusively affect humans. They can infest any person and move from one host to the next through direct (head-to-head) or indirect (via clothes) contact. This is why they are able to multiply in densely populated locations, such as schools and daytime nurseries.

Current solutions 

There is no preventive treatment or spontaneous cure. The most common method of eliminating these parasites is mechanical, by using a fine comb, in addition to applying shampoos and sprays containing insecticides. These insecticides are often very toxic and must be handled with great care, especially with children.

In addition to these essential treatments, infested sufferers often test out home remedies (applying vinegar, mayonnaise on the scalp), the efficacy and safety of which lack scientific evidence. These home remedies may eliminate some of the adult lice, but none of them remove the nits.

The use of insecticide-based anti-lice products have proven quite effective over the last few decades. However, this method is growing less and less effective as the lice become increasingly resistant to it. 

The anti-lice treatments currently available on the market are becoming less effective because head lice are growing increasingly resistant to the insecticides contained in these products.

Our solution

All animals communicate in order to find one another. Females, for example, attract males by releasing irresistibly attractive odours, which are known as sexual pheromones. This phenomenon is very common in the animal kingdom. We are currently studying the social environment these insects live in and the way they communicate. Our aim is to find ways of attracting them and eliminating them without using toxic products, much like the method we used to develop Acar’up. Once developed, these lure traps will provide an appealing alternative to insecticides. 

We are currently developing a trap, free of toxic products, that attracts and eliminates lice.

Did you know?

A ‘bubbling’ birth

Lice larva do not have beaks like chicks to burst their egg shells, so how do they hatch from their egg? Inside the nit (egg), the lice larva will reach maturity within 6-9 days. When the larvae breaks free, it starts swallowing air and excreting farting! This forms a large bubble of air, which bursts and breaks the egg shell. “This insect truly flatulates its way to life (Pray, 1999)”.

‘Lice head’ children

Everyone can catch head lice. However, some children catch them more often than others. It is likely that a person's hair thickness and the length of a louse’s pincers are the key factors determining the risk of infestation. In fact, head lice attach themselves and move around using their legs, which have pincers at the end (see photos). If the diameter of a hair strand is too thick or thin, the insect will find it difficult to move around and feed or find a louse of the opposite sex to breed with. Head-to-head transmission is therefore more difficult for them.

If a louse makes its way into a population of children whose hair is not the right diameter for its pincers, it will soon fall off and die. Consequently, in a class of children with fine, smooth hair, any surviving lice will have suitably sized pincers, which enables them to move around easily along smooth hair. A child with thick or frizzy hair in a class of lice-infested children with fine, smooth hair will probably have less chance of catching lice, and vice versa, a child with smooth hair in a class of lice-infested children with frizzy hair will be less likely to be infested by the same lice as their frizzy-haired classmates.

As such, if your child frequently catches lice, it is most probably because their hair thickness is similar to that of their infested classmates.



Do you have any questions about this project? Is your child’s hair infested with lice? Do the children in your class have lice in their hair?

Please contact the researcher in charge of this project, Alice Manghi, at the following email address This email address is being protected from spambots. You need JavaScript enabled to view it. or by telephone + 32 (0) 2 880 62 67. We will visit you at home or invite you to our laboratory so that we can help you remove these insects by combing your child’s hair and removing the adult lice from their head.

Link to find out more about pests of all kinds