Symptoms
Possible symptoms of head lice infestation include itching and skin disorders of the scalp. Lice eczema occurs mainly on the back of the neck and may be accompanied by swollen lymph nodes. A head lice infestation can also proceed without symptoms, especially in the beginning during the first weeks. The eggs and empty egg cases can be seen in the hair, especially on the back of the neck, behind the ears and on the temples. If the skin is scratched open, bacteria can enter and cause a skin infection. Head lice can also cause feelings of shame and psychosocial problems. Children who attend daycare, kindergarten, and school are most affected, but adults, such as family members, are also affected.
Causes
The head louse is an ectoparasite and a wingless insect with six legs that reaches the size of sesame seeds when fully grown (about 3 mm). The claws on its legs allow it to cling tightly to the hair. The lice live in the hair of the head on the scalp and the section of the hair near the scalp and survive there for up to four weeks. They feed on the blood that they regularly absorb from the skin. The female louse lays small eggs daily. They are attached to the hair in a chitinous sheath with a putty substance just above the scalp. The larvae hatch after about 7 to 9 days and mature into sexually mature lice within 8 to 12 days. The empty egg cases, called nits, remain on the hair for weeks and grow upwards with it. The itching is triggered by an allergic reaction and by a foreign body reaction to the components of the saliva. It occurs with a delay in the initial infestation.
Transmission
Head lice are transmitted from person to person and mainly during close body contact from hair to hair. Humans are the only host. The insects crawl and are not passed from animals. They cannot jump like fleas, fly like mosquitoes, or swim. Indirect transmission via combs, hairbrushes, headgear, bicycle helmets or pillows can occur very rarely, but is considered of little relevance. This is because lice that are not in contact with the hair quickly lose their infectivity and die within about one to two days. Also, the eggs do not develop outside the body. Therefore, environmental treatment is not considered necessary. It is known from large studies that head lice are almost never found on pillows.
Diagnosis
The diagnosis is considered confirmed when at least one live louse or viable eggs are found. Lice or eggs are found on the hair base and the section of hair near the scalp (see above). The light-shy insects are difficult to detect. The eggs are light or dark and cannot be wiped off the hair like scalp dandruff or impurities. Since they are very small, a lamp and magnifying glass should be used to help. Wet combing with a lice comb can significantly improve the reliability of the diagnosis (!).
Prevention
Transmission to other people should be prevented as much as possible. A number of medical devices, medications, and hair care products are available for prevention. There are also sprays on the market that are sprayed on the hair in the morning, so in case of an outbreak, for example, before kindergarten or school.
Non-drug treatment
Regular wet combing of the hair with a nit comb (louse comb) removes the lice mechanically. It is recommended as an adjunctive measure to treatment with the louse remedy. In principle, combing out alone without louse remedy is also suitable as a therapy method, but it is very time-consuming. The empty egg cases do not all need to be removed, as no more larvae emerge from them. Complete shaving of the hair is effective because the lice need the hair shaft to lay their eggs. However, the cosmetic result of this method is not acceptable. Killing with a hair dryer is unreliable and can cause damage to the scalp. Hygienic measures and environmental treatment are hardly considered necessary today. If desired, laundry can be washed at above 60°C and dried in a tumble dryer. Insecticide sprays are not recommended.
General treatment regimen
- Day 1: Treatment with the louse remedy, comb out wet with the nit comb.
- Day 5: Wet comb out to remove early hatched larvae.
- Day 7 to 10: Repeat the treatment with the louse agent to kill newly hatched larvae.
- Day 13 and 17: Control examination by wet combing out.
Infested groups such as families or school classes should all be treated together – that is, synchronously. It must be noted that there are carriers without symptoms. If the louse agent also kills the eggs, in principle, no post-treatment is required. This is the case, for example, with spinosad (see below).
Drug treatment
Various louse agents are available that are marketed as drugs or medical devices. The application and duration of action differ. Full details can be found in the package insert. Insecticides affect the nervous system of insects and kill them. They are registered as medicines. Increasing resistance is a problem. Not all active ingredients are effective against eggs:
- Permethrin (loxazole).
- Allethrin, spinosad, and topical ivermectin are not yet registered in many countries. Spinosad kills insects as well as their eggs.
- Abametapir (Xeglyze, USA) is an insecticidal and ovicidal agent. The effects are based on the inhibition of metalloproteases.
- Lindane (Jacutin, out of commerce) is no longer commercially available in many countries and in the EU because of the potential for adverse effects and because of environmental concerns. It should no longer be used.
- Malathion (Prioderm, out of trade) is also no longer in trade in many countries.
Physical agents:
- Such as silicone oils with dimeticone or cyclomethicone (e.g. Hedrin) are physically active pediculocides that block the oxygen supply to the insects and cause suffocation.
Herbal preparations:
- Most often contain plant extracts, fatty oils and essential oils.
Oral therapy (tablets):
- Ivermectin (Stromectol tablets) is not yet approved as a human drug in many countries. It is taken as a tablet and the lice absorb the active ingredient with their blood. The application should be repeated as for external agents.
Home remedies:
