Which is more effective against lice and nits, shampoo? - briefly
A pediculicidal shampoo containing an FDA‑approved insecticide (e.g., permethrin 1% or pyrethrin) will kill live lice but does not reliably eliminate all nits, which require mechanical removal with a fine‑toothed comb. Consequently, shampoo alone is less effective than a combined chemical treatment and combing approach.
Which is more effective against lice and nits, shampoo? - in detail
Lice‑killing shampoos contain insecticidal agents such as permethrin, pyrethrin, or dimethicone. These compounds act on the nervous system of adult lice, causing rapid paralysis and death. Dimethicone, a silicone‑based oil, also coats eggs, reducing their ability to hatch. When applied according to label directions—typically a thorough wet‑combing after a 10‑minute soak—the product eliminates most live insects in a single treatment.
Comparative studies show that shampoos with dimethicone achieve 90‑95 % eradication of both adults and nymphs, while permethrin formulations reach 80‑85 % under optimal conditions. However, resistance to pyrethroids has reduced the efficacy of permethrin in many regions, resulting in higher failure rates and the need for repeat applications.
Alternative methods include:
- Mechanical removal with a fine‑toothed nit comb, effective when performed daily for 10‑14 days.
- Prescription oral medications (e.g., ivermectin), reserved for resistant infestations.
- Over‑the‑counter lotions containing benzyl alcohol or malathion, which require longer exposure times and may cause skin irritation.
The most reliable approach combines a high‑efficacy shampoo with meticulous combing. The shampoo provides rapid kill of live lice, while the comb eliminates surviving eggs that the product may miss. For resistant cases, switching to a dimethicone‑based formula or adding a prescription oral agent increases success rates.
In practice, a single, properly executed shampoo treatment followed by a second combing session 7‑10 days later yields the highest overall clearance of both insects and their eggs.