The irritant capacity of several anionic, amphoteric and non-ionic surfactants has been studied by non-invasive techniques, specifically by evaporimetry, laser Doppler flowmetry and one-dimensional cutaneous ecography. Some of the surfactants most frequently used in shampoos and shower/foam gels were selected for testing. A series of aqueous solutions containing 5% of the active material in these products was patched onto normal skin; controls for comparison were set up with water and with sodium lauryl sulphate (SLS), a recognized irritant standard substance. It was deduced from the results obtained that, of the surfactants tested, the one showing the lowest irritant capacity is decyl polyglucoside, followed in increasing order of irritant capacity, by cocoamidopropyl betaine, magnesium laurylether sulphate and sodium laurylether sulphate.