Abstract
Cinnamic acid and its natural derivatives were primarily used in cosmetics as fragrance materials as well as skin and hair conditioners. Nowadays, not only natural but also synthetic cinnamic acid derivatives are used as active ingredients of cosmetic formulations. They still serve as fragrance ingredients but also as active ingredients supporting the treatment of selected dermatoses such as acne vulgaris, atopic dermatitis, and hyperpigmentation. They are also commonly used in anti-aging cosmetic formulations. On the other hand, several cinnamic acid derivatives used as fragrances in cosmetic products are classified as potential allergens which can cause contact dermatitis. The main mechanisms of action proved for various cinnamic acid derivatives include antioxidant, antimicrobial, anti-inflammatory, and antimelanogenic properties. Most commonly used cinnamic acid derivatives in cosmetics products are hydroxy acids such as ferulic acid, caffeic acid, p-coumaric acid, and sinapic acid. Chemical synthesis led to several modified acids, esters, and amides, which also showed the potential to be used in cosmetic formulations.