A method of repairing oxidatively-treated hair, the methods comprising the sequential steps of: (i) soaking hair in an aqueous treatment composition, (ii) rinsing the hair of step (i); characterised in that the aqueous treatment composition comprises 0.1 to 6 wt % N-acetyl amino acid, based on the total weight of the composition, wherein the N-acetyl amino acid is selected from the group consisting of N-acetyl glycine, N-acetyl alanine, N-acetyl proline, N-acetyl leucine, N-acetyl isoleucine, N-acetyl valine, N-acetyl tyrosine, N-acetyl phenylalanine, N-acetyl tryptophan, N-acetyl serine, N-acetyl glutamine, N-acetyl threonine, N-acetyl asparagine, N-acetyl methionine, N-acetyl lysine, N-acetyl histidine and mixtures thereof, gives damage repair benefits.