Clinical and laboratory trials employing carbaryl against the human head-louse, Pediculus humanus capitis (de Geer)

Carbaryl was very effective against head lice when used as a 0·5%, lotion or a 0·5%, shampoo at a dose of 50 mg active ingredient per head. Unexpectedly good ovicidal and residual effects were found, especially when carbaryl was employed as a lotion. These effects equalled those of malathion and exceeded those of gamma-benzene hexachloride (HCH or Lindane), bioresmethrin and chlorphenamidine. The ovicidal effect was also demonstrated in the laboratory, but shown to be highly thermo-labile. It was also shown that the only known form of malathion resistance in any of the human lice does not extend to carbaryl.