Comparative efficacy of treatments for pediculosis capitis infestations.

Ovicidal activity and killing times were evaluated for six pediculicides, using viable eggs and recently fed head lice from infested children. Lice were continuously exposed to the products until death, and elapsed time was recorded. Eggs were immersed for ten minutes, rinsed, and dried. Four synergized pyrethrin products (RID, R&C Shampoo, A-200 Pyrinate Shampoo, A-200 Pyrinate Liquid) killed all lice in ten to 23 minutes, and 23% to 32% of treated eggs hatched; 0.5% malathion lotion (Prioderm Lotion) killed lice within five minutes and was highly ovicidal, with only 5% of eggs hatching. One percent lindane shampoo (Kwell Shampoo) was the slowest-acting pediculicide, requiring approximately three hours to kill all lice; 30% of the eggs hatched after treatment. The in vitro results for RID, Prioderm Lotion, and K well Shampoo were validated by clinical trials.