What is benzoyl peroxide?
Considered the most effective over-the-counter choice for a topical antibacterial agent in the treatment of blemishes (Source: Skin Pharmacology and Applied Skin Physiology, September–October 2000, pages 292–296). The amount of research demonstrating the effectiveness of benzoyl peroxide is exhaustive and conclusive (Source: Journal of the American Academy of Dermatology, November 1999, pages 710–716). Among benzoyl peroxide’s attributes is its ability to penetrate into the hair follicle to reach the bacteria that cause the problem, and then kill them—with a low risk of irritation. It also doesn’t pose the problem of bacterial resistance that some prescription topical antibacterials (antibiotics) do (Source: Dermatology, 1998, volume 196, issue 1, pages 119–125). Research has also shown that benzoyl peroxide is more effective than some other prescription treatments for acne, such as oral antibiotics or topical antibiotics (Source: Lancet, December 2004, pages 2188–2195).
Using benzoyl peroxide
Benzoyl peroxide solutions range in strength from 2.5% to 10%. It is best to start with lower concentrations because a 2.5% benzoyl peroxide presents a much lower risk of potential irritation than a 5% or 10% concentration, and it can be just as effective (Source: Clinical and Experimental Dermatology, April 2014, pages 273-277). The concentration that is required depends entirely on how stubborn the strain of bacteria in your pores happens to be. Although this was once thought to be a problem, research has shown that benzoyl peroxide can, in fact, be applied at the same time as products with retinol or prescription retinoids such as Renova, Retin-A, Differin, Tazorac, and generic tretinoin (Source: The Journal of Clinical and Aesthetic Dermatology, October 2010, pages 26-28).
Benzoyl peroxide + salicylic acid?
Benzoyl peroxide works even better when combined with another anti-acne superstar ingredient, salicylic acid. It is perfectly fine to apply these ingredients at the same time, though some people may find doing so leads to unwanted side effects such as redness or flaking skin. If that happens to you, the solution is simply to apply one anti-acne product in the morning and the other at night, or you can reduce frequency of application (Sources: Journal of Drugs in Dermatology, March 2013, pages 259-264; Cutis, June 2012, pages 287-293 and July 2009, pages 48-55)