Frequently asked questions about lice

In this article, we have compiled a number of frequently asked questions about lice. You'll find answers to what lice look like, where they live, how they are transmitted, etc.

Some of the questions are accompanied by links to in-depth articles on the topic in question.

Please note that this article only deals with the three species of lice that suck blood from humans - not the other 5000 species that live on animals.



What do lice look like?

All lice have small, wingless and flat bodies with six legs (three pairs). Head lice and body lice have elongated bodies, while crabs are almost round. Head lice can be white, brownish or gray, while body lice are always brownish or grayish in color. 

The easiest way to determine which lice species is which is usually by looking at its habitat; head lice live in the hair on the head, body lice live in clothing and crabs live in the pubic hair around the genitals. However, all three lice species can, in rare cases, also migrate to other parts of the body.

Head lice are 2.5 - 3 mm long

Head lice are 2.5 - 3 mm in length and have three pairs of legs. However, nymphs can be as small as 0.5 mm.

Adult lice of different species have different sizes; head lice are 2.5 - 3 mm, body lice are 2.5 - 3.5 mm and crabs are 1.3 - 2 mm. However, it's important to note that nymphs (which are precursors to the adult lice) are smaller and can be as small as 0.5 mm in length in head lice, for example.


What do lice eggs look like?

Head lice eggs are white and oval-shaped and are attached to individual hairs on the scalp. There is only one egg per hair. Most eggs are usually found on the back of the neck and behind the ears.

Body lice eggs are also white and oval, but are found in the host's clothing - typically in seams and folds. The eggs, as well as the adult lice, can be found in places where clothing is tight to the body, such as trouser hems, bra straps and the like.

Bat eggs are in brownish sacs that are attached to individual hairs. Hatched egg sacs are white. The eggs are usually only found in pubic hair, but they are also rarely found in eyelashes, beards and other stray hairs on the body.

Read more about lice eggs here.


Hosts of lice

Can adults get lice?

Adults as well as children can get lice. However, they tend to infest children more often than adults - especially because they are in close contact with each other on a daily basis. Children between the ages of 3 and 10 are particularly affected.

Until the end of the Middle Ages, lice were a problem in practically all age groups.


Do I have lice?

If you suddenly experience severe itching on your scalp, chances are you have head lice.

If you suddenly experience severe itching on your body - especially in areas where clothing is close to your body - chances are you have body loop.

If you suddenly experience severe itching around your genitals, chances are you have crab.


Do lice only live in the hair?

Head lice live primarily in the hair on the head, but can also migrate to other parts of the body and live in the hair there. Head lice do not prefer dirty hair to clean hair. Cutting your hair short can help if you have recurring problems with head lice (however, the hair should be shorter than 0.5 cm to be sure to avoid them).

Body lice live exclusively in the host's clothing and only travel on the body when they need to suck blood.

Crabs live primarily in the pubic hair around the genitals, but can also migrate to other parts of the body such as the eyelashes, armpits or beard.



Are lice contagious?

Lice are transmitted between hosts - i.e. humans. Head lice are only transmitted through close contact (hair-to-hair), while body lice can also be transmitted via shared textiles (e.g. bedding, towels, etc.). Crabs are generally only transmitted through intimate contact.

Lice cannot be transmitted from animals to humans or vice versa. Animals are infested by lice species that live exclusively on animals.

Lice eggs are not contagious because they are attached to individual hairs and can only hatch under the right conditions (this includes temperatures above 22°C).


How do you get lice?

Lice spread easily between people. Head lice are mainly transmitted through hair-to-hair contact. Body lice are spread through close contact and shared textiles (e.g. bedding, towels, etc.). The risk of body lice is also increased if you live very close together. Crabs are mainly acquired through intimate contact.

Lice can't jump, fly or swim, and you can't get them from pets or other animals. Lice eggs are also not contagious.


How do lice develop?

Lice do not "originate" as such, but are transmitted from human to human, just like many other parasites and diseases.

Head lice and crabs are only transmitted through close contact, while body lice can also attach themselves to bedding, towels, etc. and find their way to new hosts.

Although all lice originate from eggs, lice eggs are not contagious because the eggs are attached to the host's hair and usually cannot hatch without the host's body heat. This also applies to body lice, which attach their eggs to the host's clothing fibers.


Where do lice come from?

Lice come from human hosts - meaning they are transmitted from one human to another. Head lice and crabs are mainly transmitted through close contact, while body lice can also be transmitted through textiles. 

Lice do not come from plants or animals (including pets). Lice hatch from lice eggs, but these are not contagious.



What to do when you discover lice?

Once lice are detected, treatment should be started as soon as possible. In addition, you should also inform other people about the presence of lice:

  • Head lice: If you have head lice, you should check everyone in the household and if you have children, the school, daycare center and other parents should also be made aware.
  • Aphid: If you have crabs, you should make all sexual partners aware of this.
  • Body lice: If you have body lice, wash all textiles and clean your home thoroughly. If you live very close together, see if you can find a solution to create more space.

Read more about lice treatment here.


How to get rid of lice?

Head lice can be difficult to get rid of because treatment is not always done correctly. They are most easily treated with lice repellent, but can also be removed by combing with conditioner. Read more about head lice treatment here.

Body lice are usually easy to get rid of because it's just a matter of establishing regular hygiene - i.e. showering every day, washing your clothes regularly and changing your clothes every day. Read more about body lice treatment here.

Aphids are relatively easy to get rid of because they only need to be treated with a lice repellent. Read more about treatment of crabs here.


How long should lice stay in the freezer?

The rule of thumb is to freeze clothes and bedding (that a person with lice has used) for 2 days.

However, the idea of freezing clothes and bedding only makes sense if you have body lice - which is very rarely the case. Body lice are most common in people who are unable to maintain normal hygiene and who may live very close together. Examples include refugees, homeless people, war victims, etc.

When you get lice, it's almost always head lice, which can't be transmitted via clothing or bedding anyway. This is because head lice (and crabs for that matter) cannot survive for more than 24 hours outside their host. Body lice, on the other hand, can survive for up to 1 week outside their hosts and can therefore transmit via clothing and bedding.

However, if you have body lice, it is not necessary to freeze clothes and bedding; simply wash them at 55°C (and tumble dry them if necessary), which will kill all lice and eggs. Alternatively, you can store the textiles in sealed plastic bags for 14 days, which will also kill all lice and eggs.


How to avoid lice?

Contact usLice can be avoided by avoiding close contact with people who already have lice (especially hair-to-hair contact). 

Children's: If you have children attending school or daycare, it's important to check their hair and scalp regularly for head lice. You should also be aware of the presence of lice in schools and daycare centers (outbreaks are usually announced). Head lice in children are most common between August and November and immediately after vacations.

Products and servicesThere are special preventive lice repellents that can be used to avoid lice infestations. These products can be used if you are at increased risk of getting lice (e.g. if a child in the household has lice, there are lice at school, during vacations, etc.) We recommend Linicin Prevent on the right because it contains no insecticides, is skin-friendly and odorless.

We recommend this product to avoid lice

Hair length: Hair length has a certain impact on the risk of infection, and it is a fact that long-haired children get lice more often than short-haired children. If you have been infected repeatedly, you may therefore consider cutting your hair short. However, the hair should be shorter than 0.5 cm to be absolutely sure of avoiding them.



How long can lice survive?

All adult lice have a lifespan of up to 30 days. The duration of the total life span depends on the species, as the hatching time of eggs and the duration of nymph stages vary from species to species. Read more about the life cycle of lice here.

Lice that do not sit on a host do not survive for long. The survival times for the different species are as follows:

  • Head lice = 24 hours
  • Body lice = 5 - 7 days
  • Crabs = 24 hours

Body lice and crabs rely heavily on the blood and body heat of their hosts, with body lice being more robust because they live in the host's clothing.


Can lice bite?

Lice feed by biting the skin of their host and sucking blood from it. They have mouthparts that are specially developed for this purpose.

People react very differently to lice bites. If you've never had lice, you'll usually feel no or very little irritation at the first few bites. After a short while, you typically become slightly hypersensitive to the bites and start to have an allergic reaction to them. This causes redness, itching and irritation of the skin.


What is the difference between lice and fleas?

Lice and fleas are very similar because they are both wingless parasites that can live on humans. Some of the differences are that:

  • Hosts: Lice only live on one type of host (either birds, humans, mammals, etc.), with some flea species being able to live on both mammals and humans, for example
  • MobilityFleas can jump, which lice cannot. Fleas are generally much more mobile than lice.
  • DevelopmentFlea developmental stages are more clearly divided, with distinct differences between the egg, larval, pupal and adult stages. In lice, the differences between stages are less clear and there are also fewer stages.

Lice and fleas both belong to the subclass Neopterabut belong to two different superorders (Exopterygota and Endopterygota). Below is the scientific classification of lice and fleas:

Classification Danish description
Kingdom Animalia Animals
Row Arthropoda Arthropods
Class Insecta Insects
Underclass Pterygota Winged insects
Infra class Neoptera Insects with nymph stages
Overorden Exopterygota Insects with external wings*
Medals Phthiraptera Lice
Classification Danish description
Kingdom Animalia Animals
Row Arthropoda Arthropods
Class Insecta Insects
Underclass Pterygota Winged insects
Infra class Neoptera Insects with nymph stages
Overorden Endopterygota Insects with internal wings*
Medals Siphonaptera Flea

*The development of external and internal wings is just one of the differences between lice (Exopterygota) and fleas (Endopterygota). Lice are also considered to be so-called hemimetabolous insectswhich undergoes a incomplete transformationwhere fleas are considered holometabolous insects that undergo a complete transformation.

However, these characteristics are not unique to lice and fleas, but are also found in other insects.