Compositions, kits, and methods for rebuilding the disulfide bonds in hair that is damaged due to a hair coloring treatment are disclosed. The compositions contain one or more compounds that covalently crosslink at least two thiol groups in the hair. The compositions may be applied subsequent to a hair coloring treatment or simultaneously with a hair coloring treatment. Under normal hair washing conditions, the covalent crosslinks formed are not succeptable to reduction or hydrolysis. Use of the crosslinking compositions prevent the reversion of the hairs disulfide bonds to its reduced state, for at least one week, preferably at least three months, more preferably at least one year, most preferably at least greater than one year, after at least one application of the composition.
