Serine
No meaningful concern for most people; irritation is possible but rare.
Also written as: L-Serine
What it is
Serine is one of the twenty standard amino acids and is among the most abundant components of the skin's natural moisturising factor, released when the protein filaggrin breaks down in the outer skin layer. Cosmetic serine is usually made by fermentation. Formulators add it, often with other amino acids, to top up the skin's own water-binding pool.
What it does well
Contributes to the skin's natural water-binding pool
Serine is genuinely a major part of natural moisturising factor, so replenishing it is biologically sensible. Evidence that applying it topically raises skin hydration measurably on its own is limited; it usually appears as part of an amino acid blend.
Limited evidence
Worth knowing
No meaningful safety concerns
Serine is a dietary amino acid and a normal skin constituent. It is not a recognised sensitiser and has no EU restriction.
Matters most toNo specific group.
Where the EU stands
No specific restriction
Permitted in EU cosmetics with no concentration limit. It is not listed in the banned, restricted or preservative annexes of the Cosmetics Regulation.
