Hydroquinone 4% strong inhibitor of melanin production that has long been established as the most effective ingredient for reducing and potentially eliminating melasma. Active Ingredient: Hydroquinone USP, 4% (40mg/g). Inactive Ingredients: Water (aqua), glycerin, cetyl alcohol, PPG-2 myristyl ether propianate, sodium lauryl sulfate, TEA-salicylate, latic acid, phenyl trimethicone, tocopheryl acetate, sodium metabisulfite, ascorbic acid, methylparben, disodium EDTA, propylparaben, saponins, BHT