The invention relates to a liquid mixture containing 4- (3-ethoxy-4-hydroxyphenyl) butan-2-one and a xanthine compound, as well as a cosmetic composition containing such a mixture. Application to the care, makeup and cleansing of keratin materials. L'invention concerne un mélange liquide contenant du 4-(3-éthoxy-4-hydroxyphényl )butan-2-one et un composé de xanthine, ainsi qu'une composition cosmétique contenant un tel mélange. Application au soin, au maquillage et au nettoyage des matières kératiniques.