Isoleucine is a branched-chain amino acid used in skincare as a skin-conditioning agent and humectant that helps maintain hydration and supports the skin's natural moisturizing factor. It is generally included in formulations to improve skin feel and barrier support rather than as a primary therapeutic active.
| Reported effect | How often | Notes |
|---|---|---|
Mild irritation or redness | Rare | Possible in sensitive individuals, typically transient and concentration-dependent. |
Allergic contact dermatitis | Very rare | Isolated reports; amino acids are considered low-sensitizing ingredients. |
Frequencies reflect typical cosmetic use reported in the literature, not a guarantee for your skin.
Peer-reviewed papers on this ingredient, via PubMed.