Photostability of cosmetic materials

Synopsis The basic principles of photochemistry and photochemical reactions applicable to the topic are briefly reviewed. A more detailed survey of the photochemical reactions of raw materials used in the formulation of cosmetics is treated, according to the principal chemical classification of the material. In each group the photochemical reactions of the substance are reported with the more apparent implications for the cosmetic industry highlighted. The effects of photochemical catalysts are discussed, including the sources of impurities which can catalyse photochemical spoilage of cosmetic products. The methods of retarding photochemical degradation are appraised, including precautions which could be adopted in manufacturing processes and the use of additives collectively known as antioxidants.