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Head Lice Develops Resistance to Common Treatments

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Head Lice

Head Lice

Problems with head lice? Experts say that the problem on head lice is that they are now developing resistance to standard medications. But before we proceed further in our discussion, let us first recall basic information about head lice.

Head Lice

Head lice are obligate ectoparasites with the scientific name Pediculus humanus capitis that can infect humans. They are wingless insects that often spread their entire lives on the human scalp and often feeding on human blood. They are different from fleas and they cannot fly nor jump nor walk on flat surfaces. There are two types of head louse: the disease carrying and the non-disease carrying. The disease carrying Pediculus humanus  often attaches its eggs to clothing, while the non-disease carrying type Pediculus humanus capitis attaches eggs to scalp hair.

Head lice are the subject of various eradication campaigns around the world. They are not carries of known human disease unlike body and can only cause rare secondary infections derived from bite scratching. They are rather a cosmetic problem than a real medical problem. Head lice infections may actually benefit those who want to have stability of the natural immune response against body lice which are capable of transmission of dangerous diseases.

Head lice may bring about various symptoms such as itchiness of the scalp particularly behind the area behind the ears and the nape of the neck. If the person resorts to too much scratching the person may be at risk for having secondary bacterial infection of the skin.

Head lice are transferable from person to person through direct contact and through indirect contact. Indirect contact means that head lice can be transferred through coats, hats and scarves which hang or are stored beside one another in cloak rooms or in coat racks or coat hooks. Head lice may also spread through infested hair brushes and combs which are shared by two or more persons. It can also spread when there is sharing of infested bedding, towels or shower caps. Head lice can easily spread through institutions, homes, schools or camps.

Head lice have been the center of many misconceptions among the public. The truth is that head lice do not transmit communicable diseases. These insects do not jump and fly but they can only crawl. They are completely dependent on the human host for food by feeding on their blood. Long haired people have an equal chance of acquiring head lice with short-haired people. They cannot live on the eye brows and eye lashes. Head lice can infect people of any age, socioeconomic status, sex, race or personal hygiene habits. Human lice cannot be acquired from animals.

Head lice may only up to 30 days; the female can deposit about 90 eggs in the scalp. After about 7 to 10 days, the nits can hatch and can later on turn into adults for another 10 days. Head lice can live outside the host for about two to four days at a temperature of 74 degrees Fahrenheit (F) and one to two days at 86 degrees. Nits can only live up to 10 days and cannot hatch at or below room temperature.

Head lice are traditionally treated with both prescription and over-the-counter remedies. Infested clothing should be removed and head lice medication applied according to its instructions. During treatment, the eyes should be protected with a towel. The treatment is usually repeated after 7 to 10 days.

Resistance to Head Lice Treatment

A recent study has shown that head lice now carry a gene mutation that makes them resistant to standard over-the-counter treatments. Experts say that exposure to a single treatment for many years can give rise to survival of head lice with “knockdown resistance,” in the form of the TI genetic mutation. These treatments include “pyrethroid” compounds such as permethrin. The findings of this study are published in the March issue of the Journal of Medical Entomology.

To know more about head lice and other hair problems, you can read our other articles of this site.