Ovicidal effects of a neem seed extract preparation on eggs of body and head lice.

The eggs (nits) of head and body lice (Pediculus humanus capitis, Pediculus humanus corporis) were incubated for 5, 10, 15, 20, 30 or 45 min into a neem seed extract contained in a fine shampoo formulation (e.g. Wash Away® Louse), which is known for its significant killing effects of larvae and adults of head lice. The aim of the study was to test whether the developmental stages inside the eggs are also killed after the incubation into the shampoo. It was found that an incubation time of only 5 min was sufficient to prohibit any hatching of larvae, whilst 93 ± 4% of the larvae in the untreated controls of body lice hatched respectively about 76% of the controls in the case of head lice. Apparently, the neem-based shampoo blocked the aeropyles of the eggs, thus preventing the embryos of both races of lice from accessing oxygen and from releasing carbon dioxide. Thus, this product offers a complete cure from head lice upon a single treatment, if the lice (motile stages, eggs) are fully covered for about 10 min.