Pediculosis refers to infestation by blood-sucking lice: Pediculus humanus capitis (head lice), P. humanus humanus (body lice), and Pthirus pubis (pubic or crab lice). Head lice are common in schoolchildren and spread by head-to-head contact. Body lice live in clothing seams and indicate poor hygiene/crowded conditions; they can transmit pathogens. Pubic lice are sexually transmitted and infest pubic hair and occasionally eyelashes. Management includes topical pediculicides (permethrin, pyrethrins, dimethicone, malathion), mechanical removal, environmental measures, and treatment of close contacts; oral ivermectin is an option for resistant cases.
Epidemiology and Transmission
- Head lice: worldwide; no relation to hair cleanliness; spread via close contact; fomite transmission (combs, hats) is less common.
- Body lice: associated with homelessness, poor hygiene; transmit Bartonella quintana (trench fever), Borrelia recurrentis (louse-borne relapsing fever), and Rickettsia prowazekii (epidemic typhus).
- Pubic lice: sexually transmitted; consider STI screening.
Clinical Features
- Head lice: scalp pruritus, posterior auricular and occipital areas; nits (oval eggs) cemented to hair shafts within 1 cm of scalp; secondary excoriations/impetiginization.
- Body lice: pruritus on trunk/axillae; excoriations, postinflammatory changes; lice/nits on clothing seams.
- Pubic lice: intense genital itch; blue-gray macules (maculae ceruleae); visible lice at base of hairs; can spread to axillae, beard, eyelashes (phthiriasis palpebrarum).
Diagnosis
- Visualization of live lice or viable nits close to scalp/skin.
- Wet combing improves detection for head lice.
- Differentiate nits from hair casts/dandruff (nits firmly adherent).
Management
- Head lice (Pediculus capitis)
- First-line topical pediculicides:
- Permethrin 1% lotion/creme rinse applied to washed, towel-dried hair; leave 10 minutes then rinse; repeat in 7–10 days.
- Pyrethrins with piperonyl butoxide similar regimen; avoid in ragweed allergy.
- Alternative/resistant cases:
- Dimethicone 4% lotion (suffocant; non-neurotoxic), isopropyl myristate/cyclomethicone solutions.
- Malathion 0.5% lotion (ovicide; flammable; apply 8–12 hours; age restrictions vary).
- Spinosad 0.9% topical suspension (ovicide; often no nit combing required).
- Ivermectin 0.5% lotion single application or oral ivermectin 200 µg/kg, repeat day 7–10 (off-label in some regions; avoid in pregnancy and <15 kg).
- Nit removal:
- Wet-combing with fine-toothed comb every 2–3 days for 2 weeks; helpful adjunct regardless of pediculicide.
- Environmental control:
- Soak combs/brushes in hot water (>54°C) for 10 minutes; seal unwashable items for 48–72 hours; routine environmental spraying not needed.
- School policies:
- “No-nit” policies are discouraged; children can return to school after initial treatment.
- Body lice (Pediculus humanus humanus)
- Mainstay: improve hygiene; bathe and change into clean clothes; launder clothing/bedding at ≥54–60°C and dry on high heat.
- Pediculicides rarely needed; topical permethrin for body hair if heavy infestation.
- Screen for and treat associated infections; address housing/social determinants.
- Pubic lice (Pthirus pubis)
- Permethrin 1% or pyrethrins with piperonyl butoxide to affected hair; repeat in 7–10 days.
- Alternatives: malathion 0.5%, ivermectin 200 µg/kg repeat day 7–10, or topical ivermectin/lindane where available (lindane generally avoided due to neurotoxicity).
- Treat sexual partners from the past month; screen for STIs.
- Eyelash involvement: apply ophthalmic-grade petrolatum to eyelid margins twice daily for 8–10 days to suffocate lice; avoid standard pediculicides near eyes; ophthalmology referral if needed.
- Safety and resistance considerations
- Increasing resistance to permethrin/pyrethrins reported variably; rotate to non–pyrethroid agents when failure after proper use.
- Avoid malathion near heat sources due to flammability.
- Lindane is generally not recommended due to neurotoxicity risk.
- Symptom control
- Oral antihistamines for itch; treat secondary bacterial infection with topical/oral antibiotics if impetiginized.
References (recent guidelines and key reviews)
- AAP and CDC guidance on head lice management, 2021–2024.
- Public health recommendations on body lice control and louse-borne infections, 2022–2024.
- STI guidelines for pubic lice and partner management, 2021–2024.