To the Editor.—
A detailed evaluation of the relative pediculicidal and ovicidal activity of six marketed products was presented in the March 1986 Archives.1 The study, which is an attempt to develop a standardized in vitro method of screening for pediculicidal and ovicidal activity, points out the many difficulties involved. However, the approach used by Mienking and co-workers in evaluating pediculicidal activity does not, I believe, provide a closer resemblance to natural conditions than the more commonly used method of dipping lice into the test solution for specified times followed by a water rinse. Their method does not provide coverage of the entire louse as occurs when a pediculicide lotion or shampoo is applied to a person's head. Their finding of 100% effectiveness can be attributed to the fact that they only studied potent chemicals. On the other hand, this method might be an efficient way of screening out