It is known that polyether detergents have a propensity for peroxide accumulation but the rate of this accumulation and the conditions under which it occurs are not well-appreciated. We here describe the use of the FOX (ferrous oxidation in Xylenol orange) assay as a screen for detergent peroxide accumulation. We also show that a chain-breaking antioxidant, but not a metal-chelating agent block peroxide accumulation in detergent stored in the light at room temperature.