Abstract: A method for assaying the antioxidant capacity of a skin care product, the method including preparing an emulsion base, dissolving a sample of a skin care product into the emulsion base to form a homogeneous emulsion mixture, adding a detection probe to the homogeneous emulsion mixture, adding reactive oxygen species generator and/or reactive nitrogen species generator to the homogeneous emulsion mixture, measuring the fluorescence intensity change of the detection probe in the presence of the sample over time, in the presence of the standard over time, and in the presence of a blank over time, and calculating the initial rate of oxidation of the detection probe to determine the antioxidant capacity of the sample of the skin care product.