You’ve seen stars from Katy Perry to P. Diddy to Justin Bieber talking about the skin-clearing powers of Proactiv. So is there some sort of zit-zapping fairy dust inside those bottles? Not according to some experts. “Proactiv is a good product with great marketing behind it,” says Jessica J. Krant, MD, MPH, FAAD, a dermatologist at the Art of Dermatology LLC in New York. “The Proactiv system contains nothing other than readily available, over-the-counter ingredients such as benzoyl peroxide, glycolic acid, and sulfur.” Proactiv can pin its success partly on celebrity endorsements, and also on the fact that the product instructions train the user to think of acne treatment as a daily system. “Daily use is the real secret key to the success of any acne regimen,” says Dr. Krant.