Peptides are chains of amino acids. Cosmetic chemist differentiate between peptides that are beneficial to the skin and those that are not. When a peptide is proven in laboratory testing to improve the skin in some way, it is classified as an active peptide. Among these are algae peptides, copper peptides, Colhibin, Elhibin and neuropeptides.
Peptides are small molecules that can penetrate the barrier of the epidermis and have an impact on the dermis, or deeper layer of skin. These have the advantage of producing rapid, visible changes in the appearance of the skin. Specifically, they can cause tightening and the appearance of firming in the skin.