Hydroxyproline

Hydroxyproline is a nonessential (the body makes it) amino acid used in cosmetics for its skin conditioning benefits. When used in skin care, it can be either animal-derived or synthetic.

Hydroxyproline, alongside proline and glycine, is one of the major components of collagen. It plays an integral role in collagen synthesis, collagen stability and the maintenance of collagen’s structure. This means hydroxyproline contributes positively to wound-healing, skin’s overall firmness, structure (through the extracellular matrix) and health.

When topically applied, hydroxyproline primarily works as a humectant, drawing moisture to skin and boosting overall hydration. Although hydroxyproline’s derivatives and peptides (primarily N-acetyl-L-hydroxyproline) have research proving their anti-ageing properties when used topically, hydroxyproline alone doesn’t have strong research proving such.

Outside of skin care, hydroxyproline is mentioned often in skin-improving collagen peptide supplements. When ingested, these supplements turn into hydroxyproline peptides which can help skin health and hydration, promote a youthful appearance and contribute to the creation of fibroblasts.

Use levels of hydroxyproline in skin care products range from 0.1–2%, whether rinse-off or leave-on.