Re: Reaction of benzoyl peroxide in topical skin application

Hi Stephen,

Thanks for an interesting question. I think that the answer is actually more complex than you might think. I'll answer it to the best of my ability, and then you can take a look at the PDF linked at the bottom for more (a lot more) information.

As you suggest in your question, benzoyl peroxide decomposes to two molecules of Benzoic Acid.

BENZOYL PEROXIDE	BENZOIC ACID

However, this reaction is ultimately a reduction reaction, not an oxidation reaction. In addition, the process likely involves the formation of free-radical intermediates, which oxidize bacterial molecules, killing microorganisms.

It seems that there are a great number of pathways in which this decomposition can occur, and these are detailed in Chapter 1 : Mechanisms of Decomposition of Initiatiors from the Handbook of Free Radical Initiators by E. T. Denisov, T. G. Denisova, T. S. Pokidova. There are a number of references in this chapter that should provide much more information about this reaction.

Keep asking questions!