Dermax Therapeutic Shampoo contains benzalkonium chloride, which is adsorbed on to dry skin scales, these being a feature of pityriasis capitis and other seborrhoeic scalp conditions. The scales are loosened and attain a net positive charge. In the presence of the anionic foaming agent, sodium lauryl ether sulphate, the dandruff scales are then levitated into the negatively charged surface of the foam and washed from the hair. Benzalkonium chloride also acts as a mild antiseptic, which improves clinical performance when the condition is exacerbated by the presence of microbes. The major site of action against microorganisms appears to be the cell membrane, where permeability is altered