Head pediculosis (lice infestation) is one of the most common parasite diseases in humans. Early diagnosis is important to avoid direct contagion and outbreaks. Head lice ( Pediculus humanus capitis ) live on people scalp and hair, especially in children, but can occur at any age. It is an external parasite (ectoparasite) that completes its life cycle in its only host - people - whose blood they feed on. Outside of its host, the louse does not survive for long. Only people are infested with head lice. Animals can also have lice, but these are from other species, which are not transmitted to people. Head lice is not transmitted to animals. How do we get lice? The contagion of head lice is mainly by direct head to head contact , from the infested scalp and hair to healthy ones. Transmission can also occur by sharing contaminated personal objects, for example, with the use of lice infested clothing, such as hats, scarves, sports uniforms, hair ribbons, combs, towels and brushes, or even lying in a bed, mattress or pillow. Since lice do not survive long outside their host, this is a less frequent form of contagion. How do you detect a lice infestation? A lice infestation may not cause itching or any other symptoms. Therefore, especially in children, it is very important to make a careful and regular observation of the scalp and hair and immediately treat any infestation detected. Complaints of itching and itchy lesions should raise the suspicion that are due to lice. The itching is due to the allergy to the saliva that the lice inject into the skin when they bite to eat. In more extreme cases, sleep disturbances and irritability may occur, caused by the discomfort. Differences between lice and nits Lice are grayish, crawl and hide on the head (do not fly or jump), usually in more protected and warm areas, such as the neck and behind the ears. It is usually not easy to see live lice, except in huge infestations. Nits are the eggs from which lice are born. They are oval, whitish and stick to the hair, closer to the hair root near the scalp. They are easily confused with dandruff or skin scaling. Adult lice females, which are larger than males, lay 7 to 10 eggs (nits) per day. These hatch in about 1 week, new lice reach their adult stage in about 7 days and in this stage they live for about a month. After hatching, lice need to feed on their host blood several times a day. That is why they do not survive more than 1 or 2 days outside the host. Nits do not normally hatch and die outside the host within the week if they are not at the same temperature as the human scalp. Active infestation or signs of old infestation? Nits become more yellow after hatching. They remain attached to the hair but are easier to remove. In addition to the color, also the place of the hair they are in can give an idea of the time of infestation. If there are a lot of nits and these are attached to the hair within 6 mm of the scalp, it is likely to be an active infestation, even if no lice are seen; If the nits are further from the scalp and no live lice are identified, it is likely to be an older infestation. Treating lice infestations In view of the complaints described, it is important to confirm the diagnosis and be treated. Ask your physician to guide the best treatment strategy; Close contacts, such as partners and family members, should investigate the presence of pediculosis. Even without evidence of pediculosis, people who share the same bed should undergo treatment; People without symptoms, but with signs of active infestation, should still carry out the treatment; Antiparasitic products (pediculocides) are used to treat pediculosis, usually in the form of shampoo or lotion. These are over-the-counter products sold in pharmacies and, in most cases, contain insecticides. For some products, a single application is indicated, for others the application must be repeated. It depends on the product and the effectiveness of its activity against nits and / or lice. How to apply the treatment? Apply the product according to the its label and package leaflet. When the hair is very long (below the shoulder), it may be necessary to use more than one package. Shampoo / conditioner or conditioner combinations should not be used before pediculicide. It is not recommended to wash your hair 1 to 2 days after applying a pediculicidal product. After applying the product, washed clothing should be worn. If after 8 to 12 hours of treatment, the lice appear to be active as before, it may mean that the treatment is not being effective. In these cases, ask your attending physician to see if there are any complications or if you need another type of intervention. After application, dead lice and nits and those that are still alive are removed from the head with a nit comb. This plastic or metal comb has very tight and fine teeth so that in its passage it will drag the lice and nits. Comb the hair, every 2 to 3 days, with the nit comb to remove nits and lice and regularly check for the presence of nits or lice for 2 to 3 weeks. For some products, repetition of treatment is routinely recommended after the first treatment, while for others it should only be repeated if there are surviving lice. The application of products for the treatment of lice should always be done according to the instructions in the information leaflet and with the specific recommendations of healthcare professionals. Do not forget too: If someone at home has lice, the head of all family members and close contacts must be observed and all infestation cases treated; Wash in the machine, at 60 o C, clothing, bedding and other items used by infested people in the days prior to treatment (check the labels for the possibility and temperature of washing). What is not possible to wash, dry clean or seal tightly in a black plastic bag for two weeks; Immerse combs and brushes in hot water (> 60 ° C) for 5 to 10 minutes, even if there are no visible parasites; Vacuum the floor and places where people with lice sit or lie down; If your child has lice, notify the school so that all affected children can be treated and the infestation stopped. Demystify myths! Pediculosis is not a compulsory school dropout disease. However, schools should be informed if an infestation is detected, so that other students can be treated; Having lice does not just happen on hair with poor hygiene, lice prefer clean hair. However frequent washing and brushing can help eliminate some lice; Lice do not prefer long hair to lay eggs (nits), these are placed closer to the root. However, longer hair can favor head to head contact. How to prevent a lice infestation There is no preventive treatment to avoid catching lice. Observe the children scalp and hair regularly, and if they scratch their heads repeatedly. In children who frequently appear with lice, it can be useful to keep their hair short. Avoiding head to head contact and sharing objects that may be contaminated is the best way to prevent lice infestations. References Centers for Disease Control and Prevention Direção Geral da Saúde UpToDate Author : Liliana Beirão The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
