Pediculicidal effect of herbal shampoo against Pediculus humanus capitis in vitro

Human head lice infestation is an important public health problem in Thailand. Lice resistance is increasing, chemical pediculicides have lost their efficacy and thus alternative products such as herbal shampoos have been proposed to treat lice infestation. The present study investigated the efficacy of twenty nine herbal shampoos based on zinbiberaceae plants, piperaceae plants and native plants against human head lice and compared them with malathion shampoo (A-lices shampoo®: 1% w/v malathion) and commercial shampoo (BabiMild Natural'N Mild®) in order to assess their in vitro efficacy. All herbal shampoo were more effective than commercial shampoo with 100% mortality at 60 seconds and LT50 values ranged from 11.30 to 31.97 seconds, meanwhile, commercial shampoo caused 14.0-15.0% mortality and LT50 values ranged from 83.96 to 87.43 seconds. The nine herbal shampoos from Zingiber cassumunar, Piper betle, Piper ribesioides, Averrhoa bilimbi, Clitoria ternatea, Plectranthus amboincus, Myristica fragrans, Tacca chantrieri and Zanthoxylum limonella were more effective pediculicide than malathion shampoo with 100% mortality at 30 seconds and LT50 values ranged from 11.30-13.58 seconds, on the other hand malathion shampoo showed LT50 values ranging from 12.39 to 13.67 seconds. LT50 values indicated the order of pediculicidal activity in the herbal shampoos as Z. cassumunar shampoo > P. betle shampoo > Za. limonella shampoo > Av. bilimbi shampoo > P. ribesioides shampoo > My. fragrans shampoo > T. chantrieri shampoo > Pl. amboincus shampoo. Our data showed that eight of the twenty nine herbal shampoos in this study were of high potential pediculicide to human head lice treatments for Thai children.