Ingredients Explained

What each common ingredient does, and how strong the evidence is.

Product labels list ingredients, not what they do. These articles take the common ones one at a time: what each is meant to do, how it is usually used, the irritation to expect, and how good the research behind it is.

Articles marked “Being rewritten” do not yet list their sources; the others name every source they rely on.

• What does benzoyl peroxide actually do?Well established
• Adapalene vs other retinoids, including retinolWell established
• What is niacinamide, and does it help acne?Thin evidence
• Tea Tree Oil for Acne: What Is It and Does It Work?Being rewritten
• What Are AHAs and BHAs and How Do They Differ?Being rewritten
• What Does “Non-Comedogenic” Actually Mean?Being rewritten
• What Does Azelaic Acid Do? A Plain AnswerBeing rewritten
• What Does Salicylic Acid Actually Do? A Plain AnswerBeing rewritten
• Why Do Some Acne Ingredients Cancel Each Other Out?Being rewritten