Likewise, because benzoyl peroxide is so potent, Dr. Zeichner suggests keeping a close eye on how your skin reacts to it. Although true allergies are rare, "if your skin gets red, itchy, burns, or peels, you may have developed an irritant reaction from it," he says. It's also important to note that not all skin pros swear by the stuff — some say it's so drying that it can do more harm than good, just another reason to ease in and decide for yourself if your skin reacts favorably.