[5] It has been suggested that historically, head lice infection were beneficial, as they protected against the more dangerous body louse.

[12] In Ethiopia, head lice appear to be able to spread louse-born epidemic typhus and Bartonella quintana.

[21] This is made easier by using a magnifying glass or running a comb through the child's wet hair, the latter of which is the most assured method of diagnosis and can be used to monitor treatment.

Infestations are only considered extinct if nits are more than 0.25 inches away from the scalp and nymphs and adult lice are absent.

[citation needed] The presence of nits alone, however, is not an accurate indicator of an active head louse infestation.

As long as no living lice are detected, the child should be considered negative for head louse infestation.

In times and areas when louse infestations are common, weekly examinations of children, especially those 4–15 years old, carried out by their parents, will aid control.

Clothes, towels, bedding, combs, and brushes, which came in contact with the infested individual, can be disinfected either by leaving them outside for at least two days or by washing them at 60 °C (140 °F) for 30 minutes.

[28] This is because adult lice can survive only one to two days without a blood meal and are highly dependent on human body warmth.

It is thought to work not by suffocation or poisoning, but by blocking water excretion, which causes insects to die from physiological stress either through prolonged immobilisation or disruption of internal organs such as the gut.

Head lice have demonstrated resistance to permethrin, malathion, phenothrin, and carbaryl in several countries around the world.

[11] A previous method used to delay resistance included utilizing a rotating list of recommended insecticides by health authorities.

[37] Other home remedies, such as putting vinegar, isopropyl alcohol, olive oil, mayonnaise, or melted butter under a shower cap, have been disproven.

[38] After treatment, people are often instructed to wash all bedding and vacuum all areas the head may have been, such as car seats, coat hoods, and sofas, but this is not always necessary, since adult lice will die within 2 days without a blood meal, and newly hatched lice die within minutes of hatching.

Items may also be frozen for 24 hours well below the freezing point of water to ensure that ice crystals form within the cells of the lice.

[22] Reliable data describing the usual incidence of infestation in the general public, in the average school community, or during specific times of the year are lacking.The number of cases of human louse infestations (or pediculosis) has increased worldwide since the mid-1960s, reaching hundreds of millions annually.

[6] Despite improvements in medical treatment and prevention of human diseases during the 20th century, head louse infestation remains stubbornly prevalent.

[15] High levels of louse infestations have also been reported from all over the world, including Israel, Denmark, Sweden, U.K., France, and Australia.

[27][43] The United Kingdom's National Health Service report that lice have no preference for any type of hair be it clean, dirty, or short.

[44] The number of children per family, the sharing of beds and closets, hair washing habits, local customs and social contacts, healthcare in a particular area (e.g. school), and socioeconomic status were found to be factors in head louse infestation in Iran.

[46] The California Department of Public Health indicates that chronic head lice infestation may be a sign of socioeconomic or family problems.

[15] Head lice (Pediculus humanus capitis) infestation is most frequent on children aged 3–10 and their families.

[46] Females get head lice twice as often as males,[46] and infestation in persons of Afro-Caribbean or other black descent could be rare due to difference in hair shape or width.

Such stigma is even evidenced in the English language as the term "lousy", an adjective that describes something as very poor, bad, or disgusting.

[52] Over-treatment or mismanagement of head lice, which can be driven by stigma, has important implications at the level of the individual and community.

[52] Thus, to foster a return to school in a timely fashion, these policies can encourage unsafe or harsh treatment practices, including chemicals like bleach or kerosene.

Similarly, over-treatment of head-lice using pesticide-based pediculicides has been linked to increased resistance and declining efficacy of these treatments.