A polyhydroxyl monosulfoxide surfactant, usefully employed, for instance, in a cosmetic composition such as a shampoo, a hair dye formulation or a bath foam composition, has the formula ##STR1## wherein R is selected from the group consisting of linear or branched aliphatic saturated or unsaturated hydrocarbon having 8-22 carbon atoms, alkylbenzyl having 8-22 carbon atoms and mixtures thereof, and n has a statistical mean value greater than 1 and equal to or less than 10, and preferably 2-7.