What causes lice and how to treat them? - briefly
Infestations result from direct head‑to‑head contact or sharing items such as hats, brushes, and bedding; treatment consists of applying a licensed pediculicide (e.g., permethrin or dimethicone) followed by meticulous nit removal with a fine‑tooth comb.
What causes lice and how to treat them? - in detail
Lice are obligate ectoparasites that feed on human blood. Three species affect people: Pediculus humanus capitis (head lice), Pediculus humanus corporis (body lice), and Pthirus pubis (pubic lice). Each species lives in a specific niche on the host and requires direct contact for transmission.
Transmission occurs primarily through sustained head‑to‑head contact, which is common among children in schools, daycare centers, sports teams, and summer camps. Sharing combs, hats, headphones, or pillows can also spread infestations. Body lice thrive in environments where clothing is not changed or washed regularly; overcrowded housing, homelessness, and inadequate sanitation increase the risk. Pubic lice are transmitted mainly by sexual contact, but close skin‑to‑skin contact can also be a vector.
Risk factors include:
- Age group 3‑12 years, due to frequent physical interaction.
- Group living situations (e.g., dormitories, shelters).
- Limited access to clean clothing or laundry facilities.
- Lack of routine hair‑care practices that detect nits early.
Effective management combines direct removal, chemical agents, and environmental control.
Mechanical removal
- Wet combing with a fine‑toothed nit comb, performed on damp hair after applying a conditioner, eliminates lice and nits without chemicals.
- Repeating the combing process every 2–3 days for two weeks prevents hatching of remaining eggs.
Topical pediculicides
- Permethrin 1 % lotion or shampoo, applied to dry hair for 10 minutes, then rinsed; repeat after 7 days.
- Pyrethrin‑based products combined with piperonyl‑butoxide, used according to label instructions; resistance may reduce efficacy.
- Malathion 0.5 % lotion, reserved for cases where resistance to permethrin is documented.
Prescription oral treatments
- Ivermectin 200 µg/kg single dose, with a second dose 7 days later if live lice persist.
- Oral spinosad, approved for resistant head‑lice cases, administered as a single dose.
Environmental measures
- Wash bedding, hats, scarves, and clothing in hot water (≥ 60 °C) and dry on high heat for at least 30 minutes.
- Seal non‑washable items in sealed plastic bags for 2 weeks to starve lice.
- Vacuum upholstered furniture and car seats; discard vacuum bags promptly.
Follow‑up inspection 7–10 days after initial treatment confirms eradication. If live lice are observed, repeat the chosen therapeutic regimen. Education of household members about avoiding shared personal items and maintaining regular hair checks reduces the likelihood of reinfestation.