Proline

We confirmed this ingredient's definition and its registered function in public regulatory databases, but found no published study data on how the ingredient itself acts on the skin (checked by KAIAN, September 2026). We will update this page if new reports appear.

An amino acid measured as a component of the stratum corneum's natural moisturizing factor (NMF); formulated to moisturize and condition the skin

An amino acid with a ring structure (pyrrolidine ring). Quantified as one of the NMF components in measurement studies of human stratum corneum. No human study directly showing a moisturizing effect of topically applied proline alone was confirmed (uptake into isolated corneocytes has been reported in vitro)

No public data on typical concentrations in cosmetics could be confirmed (varies by product)

No public data on the time to a perceptible effect with topical use could be confirmed

Ingredient-specific irritation data not confirmed. The US CIR Expert Panel concluded that α-amino acids are safe as cosmetic ingredients under the practices of use and concentration assessed (2013; whether this ingredient was among those assessed is unconfirmed)