And there are peptides that boost hydration levels, especially. "Keratin-based peptides can repair the skin and hair by helping with moisture and elasticity levels," Dr. Hextall told R29, which brings us on to B5. Skin expert and facialist Kate Kerr rates the essential vitamin for its humectant properties, which means it attracts and binds water to the skin, in turn improving skin hydration. If skin is adequately hydrated, it looks much plumper, fine lines are reduced and any tautness and itchiness is alleviated.