Nail-hardening treatments increase the amount of cross-linking within the keratin structure and nail softening treatments led to a reduction in cross-linking of keratin in the nails, which can be quantified by texture analysis. An increase in cross-linking causes nails to become harder and have reduced flexibility, whereas a decrease in cross-linking increases nail flexibility and reduces the incidence of nail bending fatigue.

Testing protocols using nails are sensitive to many experimental factors. TRI is able to provide expert advice on designing the best protocols and on interpretation of the data.