Head Lice: Diagnosis and Therapy

Gabriel J. Martinez-Diaz, MD; Anthony J. Mancini, MD

Dermatology Nursing

Conclusion

Head lice infestation is a common yet benign problem of childhood. Head lice may be transmitted by direct head-to-head contact or fomites, most notably hair grooming items and headgear. Although the head louse does not transmit disease, the infestation can be socially stigmatizing for both the patient and his/her family. The diagnosis is made by direct visualization of live lice or nits attached to hair shafts within 1 cm from the scalp. Treatment of head lice can be challenging. Available treatment options include over-the-counter and prescription products, as well as some alternative therapy options. Efficacy and safety should be the primary drivers of treatment choice. Education of both the family and school or day-care professionals is paramount to successfully combating the cycle of head lice transmission.

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Cite this: Head Lice: Diagnosis and Therapy - Medscape - Jul 01, 2010.

Table 1. Differential Diagnosis of Nits
Diagnosis	Comment
Dandruff	Scales throughout the scalp; may attach to hairs; easily removed
Hair casts	Keratin protein that encircles the hair shaft; may be multiple; easily removed
Piedra	Fungal hair infection; firm nodules attached to hair shafts; usually white or black in color
Hair products	For example, hair spray, mousse, gel
Psoriasis	Thickened scaly plaques usually present in scalp

Table 2. Treatments for Head Lice
Type	Treatment (Brands)	Regimen	Comment
OTC
	Permethrin 1% cream rinse (Nix)	Apply to damp hair after shampooing, leave on 10 minutes, rinse. Repeat in 7–10 days.	May cause mild irritation.
	Pyrethrins 0.33% shampoo, lotion (Rid, Pronto, A-200)	Apply to dry hair, leave on 10 minutes, rinse. Repeat in 7–10 days.	May cause mild irritation.
Rx
	Lindane 1% shampoo, lotion (None; formerly Kwell)	Apply to dry hair, leave on 4 minutes, rinse.	Possible central nervous system toxicity, seizure risk (although generally only seen with incorrect usage).
	Benzyl alcohol 5% lotion (Ulesfia)	Apply to dry hair, leave on 10 minutes, rinse. Repeat in 7 days.	Kills head lice by asphyxiation; contains no neurotoxic pesticide.
	Malathion 5% lotion (Ovide)	Apply to dry hair, leave on 8–12 hours, rinse. Repeat in 7–10 days.	Approved >6 years; vehicle is flammable.
	Trimethoprim-sulfamethoxazole (Bactrim)	8–10 mg/kg/day divided BID for 10 days	Occasionally used off-label (not FDA-approved for lice); kills symbiotic bacteria in gut of louse; risk of severe allergic drug reactions.
	Ivermectin 3 mg/6 mg tablets (Stromectol)	Single oral dose of 200 mcg/kg. Repeat in 7–10 days.	Occasionally used off-label for resistant cases (FDA-approved for strongyloidiasis, onchocerciasis); possible side effects include headache, dizziness, nausea, vomiting.
Alternative	Occlusive agents (petroleum jelly, olive oil, mayonnaise, others)	Applied and usually left on overnight, then rinsed out.	No conclusive evidence-based data on the effectiveness or safety of these treatments.

Notes: OTC = over-the-counter; Rx = prescription; BID = twice daily.

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Head Lice: Diagnosis and Therapy

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