The cosmetic and dermatological potential of keratin hydrolysate

Summary Background Although keratin hydrolysates have become established as standard components in hair and nail cosmetics, studies on the moisturizing effects of keratin hydrolysates do not appear among contemporary literature. Objectives To test if adding keratin hydrolysate into an ointment base increases hydration of the skin and improves skin barrier function, or diminishes trans‐epidermal water loss. Methods Formulations were prepared containing 2%, 4%, and 6% keratin hydrolysates (based on weight of the ointment base). The moisturizing properties of keratin hydrolysates were tested by measuring skin hydration, trans‐epidermal water loss and skin pH ; measurements were carried out at intervals of 1, 2, 3, 4, 24, and 48 h. Testing was conducted on 10 women. Results As regards hydration, adding 2% keratin hydrolysate to the ointment base is optimal, as an increase of 14%‐23% occurs in hydration of the stratum corneum. For trans‐epidermal water loss, adding 4% KH to the ointment base is preferential, as this triggers a 26%‐46% decrease in trans‐epidermal water loss. Conclusions Keratin hydrolysate acts as a humectant (it binds water from lower layers of the epidermis to the stratum corneum) as well as an occlusive (it reduces trans‐epidermal water loss). The highly favorable properties of keratin hydrolysates are attributed to the wide distribution of keratin hydrolysates molecular weights; low‐molecular weight fractions easily penetrate the SC , while high‐molecular weight fractions form a protective film on the epidermis. Adding keratin hydrolysates to the ointment base did not cause phase separation even after 6 mo storage.