Leucine is a branched-chain essential amino acid used in skincare primarily as a skin-conditioning agent and humectant that helps support the skin's natural moisturizing factor. It is generally included at low concentrations as a supportive or formulation ingredient rather than a primary treatment active.
| Reported effect | How often | Notes |
|---|---|---|
Mild skin irritation | Rare | Occasional redness or stinging, typically in sensitive or compromised skin. |
Allergic contact dermatitis | Very rare | Isolated hypersensitivity reactions reported; uncommon for amino acids. |
Frequencies reflect typical cosmetic use reported in the literature, not a guarantee for your skin.