Unnatural, hygroscopic amino acids are useful to enhance the moisture retention and uptake properties of skin. In particular, such amino acids are N-hydroxyserine, N-hydroxyglycine, L-homoserine, alpha-hydroxyglycine, 2-(aminooxy)-2-hydroxyacetic acid, 2-hydroxy-2-(hydroxyamino) acetic acid, 2-(aininooxy)acetic acid, and combinations thereof.