A hair straightening or styling composition provided herein comprises: (i) citraconic acid; (ii) (a) a reducing agent and/or (b) an aldehyde, a thioacetal, a ketone or an alcohol; (iii) a buffering agent; (iv) an oxidizing agent; (v) optionally a carboxylic or dicarboxylic acid; and (vi) at least one solvent. Also provided herein is a method of straightening or styling hair using such composition.