The object of the invention is a composition for permanent waving of human hair comprising, as sole or main reducing agent one or several polyglycol monothioglycollates or lactates of the general formula ##STR1## wherein R denotes a hydrogen atom or a methyl group, X represents an ethoxy or propoxy group, and n is a number from 2 to 5. These compositions have a low characteristic smell, good waving properties, and an extremely low skin sensitizing potential.