head lice

and Martina Feichter, medical editor and biologist

Marian Grosser studied human medicine in Munich. In addition, the doctor, who was interested in many things, dared to make some exciting detours: studying philosophy and art history, working on the radio and, finally, also for a Netdoctor.

More about the experts

Martina Feichter studied biology with an elective subject pharmacy in Innsbruck and also immersed herself in the world of medicinal plants. From there it was not far to other medical topics that still captivate her to this day. She trained as a journalist at the Axel Springer Academy in Hamburg and has been working for since 2007 - first as an editor and since 2012 as a freelance writer.

More about the experts All content is checked by medical journalists.

Head lice are widespread worldwide and are always a problem in German kindergartens and schools. But how do you recognize an infestation at an early stage and what is the best way to combat head lice? Here you can read everything you need to know about it.

ICD codes for this disease: ICD codes are internationally recognized codes for medical diagnoses. They can be found, for example, in doctor's letters or on certificates of incapacity for work. B85

Head lice: quick reference

Appearance: up to 3 millimeters in size, flat, color translucent-whitish, gray or brownish; the eggs (nits) are up to 0.8 millimeters in size, oval, initially translucent, later white
Transmission: mostly directly from person to person with close physical contact; less often indirectly via objects such as hairbrushes or hats; NO transmission by pets!
Symptoms: severe itching of the head (often restless sleep as a result), possibly crimson small papules at stitches; scratching the scalp can cause skin inflammation, eczema-like rashes and additional bacterial infection
preferred locations: on the head in the temple area, behind the ears, in the neck and on the back of the head
Treatment: The best combination therapy consisting of wet combing (with a lice comb and possibly a magnifying glass) and insecticide application.

This is how you can spot head lice

A full-grown head louse is about two to three millimeters in size, flat and translucent in color from whitish to gray or brown. Because head lice adapt their color to the host's hair color over the long term, mainly brown head lice occur in populations with dark hair color and often see-through or whitish parasites in people with blond hair. When a head louse has sucked blood, however, it appears reddish because the blood shimmers through its chitin shell.

The eggs are oval, about 0.8 millimeters long and protected by a chitin shell (nit). Initially the nits are translucent, later (when the larva has hatched) white. They stick to the hair near the scalp.

A head louse infestation is often discovered by chance, for example if a few of the parasites fall out of the hair while combing. The diagnosis is therefore very rarely made by the doctor, but mostly by the parents or occasionally by educators / teachers.

Tools: magnifying glass and lice comb

Often there is already a suspicion that someone has head lice - either because of the symptoms or because cases of lice infestation are already known in the immediate vicinity. Then the head can be searched systematically for the animals. Aids such as a magnifying glass and a lice comb are advisable for this.

But first you should moisten your hair. You may also want to treat them with conditioner to make them easier to comb. It also makes it easier to see where you've already combed. Pre-combing the hair with a normal comb or brush also makes the job easier.

Then you should carefully comb through all the hair with the lice comb, the prongs of which should touch the scalp with each stroke. The head lice as well as their eggs (nits), which adhere to the hair near the scalp, get caught between the very close prongs (distance: 0.2 to 0.3 mm). This way they can be combed out and identified more easily. This is best done by wiping the comb off on a piece of kitchen or toilet paper after each stroke and then washing it.

The nits are easiest to find behind the ears and in the neck.

Young head lice that are still in the nymph stage can be seen particularly well with a magnifying glass. It is easy to overlook them with the naked eye. The magnifying glass also helps to distinguish head lice and their eggs (nits) from dandruff.

Head lice: treatment

"The child has head lice - what to do?" Countless parents ask themselves this question. The classic head lice treatment is wet combing, ideally in combination with the use of an insecticide. Alternative head lice products contain silicone oils or vegetable oils. Some people also rely on home remedies for head lice.

Wet combing

The lice comb is not only used for diagnostic purposes - it can also be used to fight head lice. To do this, the hair is made wet and possibly treated with a hair conditioner to make it easier to comb. Then comb them out thoroughly, strand by strand, with the lice comb. The whole thing should be repeated several times. In a study, "wet combing" on days 1, 5, 9 and 13 removed head lice in around 57 percent of the participating children. On day 17 you should check whether you really got rid of the parasites.

One combats head lice, for example, by making the hair wet and treating it with a hair conditioner. Then you comb them out thoroughly strand by strand with the lice comb.

This method of head lice treatment is time-consuming and requires a lot of patience on the part of the person being treated and the "practitioner". But this is often difficult, especially with children. In addition, the head lice can often not be completely removed simply by combing them out. Therefore, it is better to combine mechanical therapy with locally applicable remedies against head lice.

Head lice remedies

There are various means of treating head lice that are based on insecticides, silicone (Dimeticon) or contain vegetable oils. They are available as a tincture, spray, or shampoo. The following applies to all products:

None of the head lice remedies is 100 percent effective. Each must therefore be applied several times.
The agents can temporarily irritate the skin and cause itching.
Agents in spray form could be inhaled and then possibly trigger allergic reactions. They are therefore not suitable for children with respiratory diseases such as asthma (solutions or gels against head lice should be preferred here).

insecticides

The insecticides used against head lice in Germany include the synthetically produced active ingredients allethrin and permethrin as well as the active ingredient pyrethrum, which is obtained from certain types of chrysanthemum. They damage the parasites' nervous system and thereby kill them.

The insecticides against head lice have to be applied several times (usually after seven to ten days) in order to be successful. The exact application depends on the respective product. Before starting treatment, read the instructions for use and adhere to them, especially with regard to the exposure time and duration of use of the agents. Otherwise it can happen that some head lice or larvae and eggs survive.

Insecticides against head lice are not suitable during pregnancy and breastfeeding, with MCS syndrome (multiple hypersensitivity to chemical substances) and with allergies to chrysanthemums. Here the head lice treatment should only be done by wet combing out.

Silicone oil

Insecticides have been used against head lice for decades, including in other European countries. As a result, the head lice have developed resistance to some insecticides. That is why agents with silicone oil (Dimeticon) are now used, which are insecticidal and therefore do not cause any problems with resistance.

Head lice remedies with dimethicone are applied to dry hair and scalp and distributed well. The oil layer also covers the head lice and nits, causing them to suffocate. Sometimes you have to leave the product on overnight, sometimes just ten minutes. The exact application depends on the respective product and can be found in the instructions for use.

You should also pay particular attention to the warning notices: Agents containing silicone are easily flammable. After application, the child should therefore not stay near open flames and also not use a hairdryer!

Dimeticon is considered non-toxic and is not absorbed into the body through the skin.

Vegetable oils

Herbal remedies for head lice contain vegetable oils such as coconut oil, anise oil or neem oil (neem tree oil). The application differs from product to product - as does the mechanism of action. Some vegetable oils are said to suffocate the lice, others kill the parasites like a neurotoxin.

Recommended: comb out and combine insecticide!

Experts recommend combining combing with the use of an insecticide against head lice. This should show the best success rate in head lice treatment. The prerequisite for this is that the insecticide is used correctly in accordance with the instructions for use and the lice comb. If you are unsure, it is best to go to the pharmacy or your doctor for advice.

The following treatment regimen is recommended:

Day	measures
day 1	Treat the hair with an insecticide and then comb it while wet.
Day 5	Comb the hair while wet to remove early hatched larvae.
Day 8, 9 or 10	Treat the hair again with an insecticide to kill late hatched larvae.
Day 13	Check-up by wet combing.
Day 17	Possibly the last check-up by wet combing.

Research: the plasma lice comb

In order to be able to kill head lice without chemical agents and lengthy procedures, researchers at the Application Center for Plasma and Photonics at the Fraunhofer Institute for Layer and Surface Technology IST developed a plasma lice comb. In the housing of the battery-operated comb, pulses are generated and sent to the comb teeth, which act as electrodes. The air between the electrodes (the teeth of the comb) is ionized, creating plasma (this state of aggregation generally occurs when energy is supplied to a gas or gas mixture). In tests, the cold plasma killed the head lice and nits without harming the hair or scalp. In this way, half of the insects should be dead after a single application. The researchers say that you can get rid of all head lice within a day.

Home remedies for head lice

Anyone concerned about the possible side effects of insecticides or silicone oil will gladly resort to alternative treatments for head lice. Home remedies such as essential oils (for example tea tree or lavender oil) and vinegar should be able to fight the parasites effectively.

The essential oils may block an important enzyme in lice's metabolism, although the exact mechanism is not yet known. There are also only a few studies to date on the effectiveness of such head lice home remedies.

The effectiveness of vinegar against head lice has also not been proven. In any case, it is recommended to leave the vinegar on the hair for half an hour after applying it and then wash it off.

Other home remedies for head lice include, for example, alcohol, aloe vera and sodium bicarbonate. Here, too, the effectiveness has not been proven. The same applies to sauna stays, which are sometimes recommended against head lice infestation.

Does the rest of the family need treatment too?

If a child has head lice, all members of the family should be checked for the parasite, preferably by wet combing. Only those who are also infected should be treated.

Head lice: causes and risk factors

While clothes and pubic lice have become rare in Germany, head lice still populate human hair, especially in children. Head lice infestation (pediculosis capitis) occurs again and again, especially in kindergartens and schools, whereby hygiene does not play a role. The parasites don't care if their hair is clean or dirty. That means: Even if you wash your hair every day, head lice can lodge in it.

This almost always happens through direct transmission of head lice from person to person, for example when children stick their heads together while playing. The parasites then migrate from hair to hair - they cannot jump.

Occasionally, head lice are also transmitted indirectly via objects that have been used together within a short period of time, such as hats, combs or bicycle helmets. Very often, however, this does not happen because head lice without a host are quickly weakened and die due to a lack of blood meals. At room temperature, they usually survive on objects for a maximum of two days (in exceptional cases three days).

Incidentally, contrary to popular belief, pets are not carriers of head lice!

Where do the head lice prefer to sit?

The head lice especially like to romp around on the temples, behind the ears, in the neck and on the back of the head. Here the skin is very thin and has the optimal temperature for the little bloodsuckers.

Usually the head lice infestation is limited to the hair on the head. If the infestation is severe, the small parasites can sometimes also be found on other hairy parts of the body - in the eyebrows, armpit hair or in the beard.

Occasionally, head lice are also referred to as hair lice, although this term is misleading and, strictly speaking, wrong, since ultimately all human lice are "hair lice" (including pubic lice, for example).

How do head lice feed and multiply?

The head lice feed on human blood. To do this, they pierce the smallest blood vessels (capillaries) in the scalp every four to six hours and then suck up the escaping blood. The saliva that the animals release into the small wound prevents it from coagulating immediately.

Head lice life cycle

After the lice have stuck the nits to the hair, it takes 7-9 days for the larvae to hatch. After a further 9-11 days, the larvae are again sexually mature and continue to multiply.

The food available at all times allows the head lice to reproduce diligently: the females can produce 90 to 140 eggs during their four-week lifespan. They lay the eggs around 17 to 22 days after fertilization: they attach them to the hair near the scalp with a special secretion. This "glue" is insoluble in water, so that the eggs do not peel off during normal hair washing.

The eggs are oval, about 0.8 millimeters long and have a chitin shell (nit). The larvae (also called nymphs) usually hatch from them seven to eight days after being laid. These develop into sexually capable adult head lice within nine to eleven days. It takes a total of around three weeks from the freshly laid egg to the reproductive louse.

Why do head lice mostly affect children?

Head lice infestation is particularly common in children between the ages of three and twelve. The reason: They have more close physical contact than adults when they play and romp around every day. This makes it very easy for the lice to change hosts. Adults rarely become infected, and when they do, it is mostly with their children who bring head lice home from school or other community facilities.

Head lice: symptoms

The head louse is no longer dangerous for the host, but it is a nuisance. Often intense itching forces those affected to constantly scratch their heads. The reason for this is the head lice's saliva, which they release into the small wounds they have made so that the blood does not clot so quickly. It provokes a local immune reaction: the body reacts to the foreign saliva with itching and the formation of crimson papules at the sting point.

Frequent scratching of the head can leave scratch marks that can even bleed. This skin damage can easily become infected, which can lead to an eczema-like rash ("lice eczema"). In addition, bacteria can easily settle on the damaged scalp. This bacterial superinfection can cause the lymph nodes on the head and neck to swell.

Because of the itching, those affected often sleep very restlessly.

Head lice: mandatory notification

Parents whose child is found to be infested with head lice must immediately inform the community facility (such as kindergarten, school) in which the child is staying. This in turn informs the health department (without naming the child) and takes measures to prevent the head lice from spreading.

A child with head lice infestation must stay at home as long as it is contagious, that is, as long as no treatment has been received. It is only allowed to visit the community facility again after the initial treatment has been carried out correctly. The parents must provide proof of treatment. How this proof should look like depends on the community institution. Sometimes a doctor's certificate is required, in other cases written or verbal confirmation from the parents about the head lice treatment carried out is sufficient.

In fairness, parents should also inform everyone with whom the child has close contact about the head lice infestation. These can be playmates (or their parents) or members of the child's sports club, for example.

Head lice: prognosis

Head lice are bothersome but harmless. In our latitudes they cannot transmit diseases. If you carry out the treatment correctly and consistently, you will get rid of the head lice quickly.

In addition to physical symptoms such as itching and scratched skin, there is sometimes a psychological burden for the entire family. This is because in society an infestation with the parasites is often associated with a lack of hygiene, although it has been proven that this plays no role in the infection.

Prevent head lice

Head lice are difficult to prevent because they spread so easily. If, however, an infestation is known in the immediate vicinity (family, community facility, sports club, playmates, etc.), you should avoid physical contact with the person concerned if possible and not use hats, scarves, combs, brushes, etc. together.

A "preventive" head lice treatment for all family members when someone is infected is not generally recommended.