4-(1-Phenylethyl)resorcinol (4-(1-Phenylethyl)benzene-1,3-diol) is a skin brightening agent that is a cosmetic additive. It works by inhibiting melanin production, reducing the appearance of dark spots, hyperpigmentation and uneven skin tone, and brightening the skin tone to reduce dullness.4-(1-Phenylethyl)resorcinol is generally regarded as safe in the cosmetic industry, and is widely used in several countries and regions.