The doctors' secret weapon? Benzoyl peroxide . That's right: the stuff we've used for ages to kill acne-causing bacteria. The main ingredient stays the same, but according to the brand, it's the way it's been formulated that may bring acne to its knees once and for all. The new Rodan + Fields Spotless two-step system for teen acne — which will be sold as a bundle — pairs a high-dosage 5% benzoyl peroxide face wash with a treatment that dispenses oxygen-boosting gel and 2.5% benzoyl peroxide in twin chambers. The breakthrough is in the gel format, which works to liquefy large, crystallized benzoyl peroxide molecules so that the ingredient is better able to penetrate the skin.