Phenylethyl Resorcinol

Phenylethyl resorcinol (Symwhite 377) is a synthetic resorcinol derivative modelled on pine-bark antioxidants and refined into one of the most potent cosmetic tyrosinase inhibitors — in vitro testing suggests strength orders of magnitude beyond arbutin-type brighteners. Clinical studies show visible reduction of hyperpigmentation and brighter, more even tone at 0.5–1%. It also carries antioxidant activity protecting the formula and the skin. Caveats: it can oxidise to a pinkish tone in poorly stabilised formulas, and concentration limits apply. Best paired with niacinamide or tranexamic acid for multi-pathway pigmentation control.