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.