However, the number of cases of human louse infestations (or pediculosis) has increased worldwide since the mid-1960s, reaching hundreds of millions annually.

These methods include chemical treatments, natural products, combs, shaving, hot air, and silicone-based lotions.

[4] Insecticides used for the treatment of head lice include lindane, malathion, carbaryl, pyrethrum, piperonyl butoxide, permethrin, phenothrin, bioallethrin, and spinosad.

[9][10][11] A 2021 systematic review and meta-analysis found that the mean frequency of pyrethroid resistance of lice was 77% globally, and even 100% in several countries (Australia, England, Israel, and Turkey).

[16] Agents approved by the FDA for treatment of pediculosis include abametapir,[17] topical ivermectin lotion, lindane, malathion, permethrin, and piperonyl butoxide with pyrethrins.

Data from a primarily American study during 1998–1999 found that no-nit policies were present at 82% of the schools attended by children suspected of louse infestation.

[28] A separate 1998 survey revealed that 60% of American school nurses felt that "forced absenteeism of any child who has any nits in their hair is a good idea.

[27] This has led to the perception that the no-nit policy serves only to ease the workload of school nurses and punish the parents of infested children.

[30][34] For example, a 1998 Israeli study found that 76% of live lice infestations were missed by visual inspection (as verified by subsequent combing methods).

[35][36] Although lice cannot fly or jump, they are fast and agile in their native environment (i.e., clinging to hairs near the warmth of the scalp),[30] and will try to avoid the light used during inspection.

[43] Other home remedies such as putting vinegar, isopropyl alcohol, olive oil, mayonnaise, or melted butter in the hair have been partially disproven,[44] The use of plastic bags may be dangerous.

[45] Similarly, the Centers for Disease Control and Prevention reports that swimming has no effect on treating lice, and can in fact harm the treatment by commercial products.

These fumes can ignite due to the presence of even a small spark or open flame - such as those caused by electrical appliances, cigarette lighters, or pilot lights in stoves and water heaters.