A hair treatment composition for straightening hair. The composition comprises: i) 0.1 to 7.9 wt % of the total formulation of a sugar lactone; and ii) cationic surfactant of formula (1): [N(R1)(R2)(R3)(R4)]+(X)− in which R1, R2, R3, and R4 are independently selected from (a) an aliphatic group of from 1 to 22 carbon atoms, or (b) an aromatic, alkoxy, polyoxyalkylene, alkylamido, hydroxyalkyl, aryl or alkylaryl group having up to 22 carbon atoms; and X is a salt-forming anion selected from halogen, acetate, citrate, lactate, glycolate, phosphate nitrate, sulphate, and alkylsulphate.