The head louse is a gray to light brown insect, which belongs to the family of human lice (Pediculidae). In a head lice infestation (Pediculosis), the head lice nests in the human scalp hair and feeds there on blood. The head lice can be 2.5-3.5 mm long and can therefore be seen with the naked eye.
A temperature of about 28 °C offers the head louse optimal conditions for survival, so that the hairy scalp is a suitable habitat. With its projection on the head, the head louse stings into the human skin and thus feeds on the blood it has collected according to the principle of a capillary. The head lice secrete saliva, which stops the blood clotting and thus keeps the blood fluid.
The head louse is able to lay up to 10 eggs (nits) per day. The eggs are placed exclusively at the hair root, especially in the neck and back of the ear. This ensures a safe source of nutrition for the hatching larvae, since the blood can be reached particularly easily at these places.
The larva (nymph) hatches from the nest after about 7-10 days. This larva also needs about 10 days before it is sexually mature and thus continues its reproduction cycle. It is important for the larva to be close to a rapid blood source, because without blood the larva dies after one to two hours.
With a total of 14 to 21 days, the reproduction of the head louse is quite fast. A male head louse lives for about 15 days. Unlike these, the survival time of a female head louse is about one month, provided that she gets blood every 2 to 3 hours.
A head louse infestation is basically and most frequently caused by direct contact with infected scalp. Situations that allow such close contact increase this probability. Especially children in schools and kindergartens are affected.
Indirect transmission is not as frequent, but cannot be completely ruled out. This mainly includes objects such as pillows or brushes that catch the affected hair. However, since the head louse does not find a food source in this case, it dies quickly and does not offer any lasting danger of infection.
It is also generally known that head lice is not transmitted via pets. Sometimes, diseases such as spotted or five-day fever or tularaemia can be transmitted with head lice. It is important to pay attention to the accompanying symptoms parallel to the head louse infestation and to consult a doctor.
However, diseases transmitted by head lice are very rare in Europe, unlike in developing countries. The assumption that head lice infestation is caused by lack of hygiene is a misconception, because head lice is found in both washed and unwashed hair. Anyone can be affected by a head lice infestation.
In general, it can be said that head lice occurs more often in children than in adults, as this is related to the age-specific behavior in schools and kindergartens, which facilitates head lice transmission. It has been found that especially in summer, children are more often affected by head lice. This is explained by the fact that summer vacations are spent in vacation homes, for example, where the close living together of different children facilitates head-to-head transmission.
If there is a noticeable scratching of the scalp, the possibility of head lice infestation should be considered and investigated immediately. Head lice infestation can be detected directly and indirectly. As a direct diagnosis one tries to find the head louse in the hair.
However, this is difficult, because the head louse moves quickly and hides itself in the light. One method, however, would be to wash the hair with a shampoo, in which the lice cannot move. The hair is combed into strands with a special comb, which is wiped off on a white cloth.
In this way the head lice can be recognized on a white background as soon as they are present. Indirectly, head lice infestation is detected by finding nits, i.e. the head lice eggs. A magnifying glass can help with this.
Nits are characterized by the fact that they stick to the hair shaft at the hair root and cannot be removed. They have a scale-like brown form. If nits are found more than 1 cm from the scalp, the nits are already empty or dead.
However, it indicates a head lice infestation some time ago.Head lice infestation is usually asymptomatic and is not always necessarily recognized or detected. However, itching of varying degrees is characteristic, especially in the rear ear and neck region, which is usually an indication of head lice infestation. It occurs as an immune response to the saliva and excrements of the head lice.
The itching can be accompanied by small reddish spots in the same region. Scratching the itchy skin can lead to inflammation of these spots. Adhesive nits with a high infestation can mat the hair.
An effective therapy of head lice infestation consists of several aspects. Not only one of the therapy options should be used, as head lice infestation can be effectively and efficiently combated and recurrence reduced by applying several therapies. Chemical therapy involves controlling head lice with insecticides, pediculocides, which can be purchased in pharmacies.
It is recommended that a family doctor or pediatrician be consulted if head lice infestation is suspected, who can then prescribe appropriate remedies, especially in the case of infants or small children. The chemical substances exist in different forms: Shampoo, spray or gel. The exact dosage of the remedies is important to achieve effective control.
In general, a single application of insecticide is sufficient to reduce the risk of infection. However, it is recommended to repeat this treatment after 8 to 10 days to ensure that any head lice that may have hatched are also combated. Pregnant women or nursing mothers should especially inform themselves about a suitable remedy, because with the frequently used remedy Permithrin it cannot be excluded that it may have a harmful effect on the child/embryo.
Parallel to the chemical application, mechanical therapy should be carried out. With a special nit comb the affected hair should be combed intensively and repeatedly wet. It is important that the distance between the teeth of the comb is about 0.3 mm, so that the smaller nits or larvae can be combed out.
It should be combed out at least four times within two weeks. More frequent use does not hurt either. On the fifth day, wet combing should be done again to ensure that any head lice that have hatched out of the hair have been removed.
After about two weeks, the hair can be combed out again wet for checking. If a head lice infestation is still detected after this time, this may be due to resistance of the head lice to the insecticide, or to a different dosage and not exact distribution of the substance in the hair. A too short application time of the preparations or the forgotten repeat treatment also leads to a returning head lice infestation.
Medicines tested by the authorities to combat head lice are mainly based on the effect of pyrethrum extract from chrysanthemum flowers. The effect of this extract attacks the nervous system of the head lice. This immobilizes the head louse and during the time of exposure, the insect is damaged to such an extent that it dies.
Side effects of this insecticide are reduced due to its sensitivity to light and oxygen. Residual substances in the hair are thus quickly eliminated from the hair, so that no consequences follow for the hair and scalp. Mixed preparations from the extract with additives, such as alcohol, also act on the nits and cause them to die.
However, since these therapies are generally not specialized on nits and therefore do not kill them effectively, the secondary treatment, which has already been mentioned, is of enormous importance. Besides these natural products, there are also synthetically produced substances. They often have a long-term effect and are less targeted at nits than at living larvae and lice, which hatch from their nits for a few days afterwards.
In the wide variety of drugs and medical products on the market, you should consult your doctor or pharmacy to find out about the correct and, above all, tested product. If someone in a household is affected by head lice infestation, it is recommended as a preventive measure to inform and examine the members living in the household and other contact persons, e.g. in kindergarten. Here it is also suggested to carry out a prophylactic head louse therapy.Cleaning of brushes and combs for affected persons is useful to avoid even minimal risks of infection.
It makes sense for each family member to have their own brush and comb. In principle it is sufficient to vacuum the apartment thoroughly. However, a complete sterile basic cleaning is not necessary.
Hair-collecting textile goods, such as pillows and soft toys, can be washed at 60°, deep-frozen or even put away for a few days. Any head lice caught in them will die off and there is no longer any risk of infestation. Prevention in public facilities is legally prescribed.
This means that in the event of a head lice infestation, the community facility should be informed immediately, especially schools and kindergartens. These then report this to the public health department. This may sound deterrent, but it has no negative consequences and need not cause any concern.
The affected person should avoid public institutions as long as they are contagious. For this time there is no obligation to obtain a medical certificate. Since there is actually no longer any risk of infection after the first treatment, it is sufficient, for example, for school to write a parental excuse.
After the treatment, school life can be resumed. This also applies to all other institutions. A general prophylaxis should take place by extending education in the form of parent-teacher evenings or flyers to raise awareness of the detection and treatment of head lice infestation.
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