The present results support that UV irradiation raises the solu- bility of hair proteins, presumably, due to the cleavage of disulfide bonds.The increased SH content has been registered in the frac- tions of the proteins eluted from hair fibers and of the soluble pro- teins resulting from hair homogenizing. Protein elution resulted in the more prominent loss of thiols from irradiated hair fibers if compared with non-irradiated samples. As a result, the thiol con- tent of the residual soluble proteins decreased after irradiation and elution of the hair. This is a possible way that could influence hair structure via cystine/cysteine modification.