Methylmethionine (S-methylmethionine, also known as vitamin U) is a methionine derivative used in skincare for its purported soothing, antioxidant, and barrier-supporting properties. It is sometimes included in formulations targeting irritated or sensitive skin.
| Reported effect | How often | Notes |
|---|---|---|
| Mild transient skin irritation | Rare | Occasional redness or stinging upon topical application, typically resolving quickly. |
| Contact allergic reaction | Very rare | Hypersensitivity responses are uncommonly reported and poorly documented in literature. |
Frequencies reflect typical cosmetic use reported in the literature, not a guarantee for your skin.