5-Ureidohydantoin (allantoin) is a naturally occurring compound used in skincare for its soothing, moisturizing, and mild keratolytic properties, helping to promote skin smoothness and support barrier repair. It is widely regarded as gentle and non-irritating across a broad range of formulations.
| Reported effect | How often | Notes |
|---|---|---|
Mild skin irritation or redness | Rare | Generally well tolerated; transient irritation occasionally reported, often related to other formulation components. |
Contact dermatitis / allergic reaction | Very rare | Hypersensitivity is uncommon but possible in predisposed individuals. |
Itching or stinging on application | Rare | Typically mild and self-limiting, more likely on compromised skin. |
Frequencies reflect typical cosmetic use reported in the literature, not a guarantee for your skin.