Mostly used as a topical treatment for mild acne since the 1920s, benzoyl peroxide is an antispectic that reduces surface bacteria on skin. It's also an oxidising agent that combats blackheads. It is safe for adults and children when used as a gel or lotion for treating spots. Benzoyl peroxide, like most peroxides, is a bleaching agent, so it's also used as a food additive in flour. It oxidises flour's carotenoids, whitening it. When the flour is made into a food product, most of the benzoyl peroxide is converted to benzoic acid, which is a commonly used preservative.