CUMULATIVE IRRITANCY IN MAN TO SODIUM LAURYL SULFATE - THE OVERLAP PHENOMENON

Repeated contact of skin with surfactants causes irritation often char acterized by dryness, erythema and scaliness. Morphologically healed s kin after preexposure can still evoke a stronger reaction to any subse quent exposure of an irritant. Cumulative irritancy using the overlap phenomenon was studied. The effects of repeated and prolonged applicat ion of sodium lauryl sulfate (SLS) on human skin in vivo (healthy adul t volunteers) were evaluated using non-invasive techniques of TEWL and skin capacitance measurements and visual scoring. The inability of TE WL and skin capacitance to achieve pretreatment values 2 weeks post SL S treatment suggests the possible detrimental effects of SLS on skin l ipids. The surfactant effect was cumulative and dehydrating effects on prolonged and repeated application were observed.