Actives glossary
The ingredients, one page each
What the ingredient is called on a label, the concentrations that actually appear on shelves, and the claims it cannot support.
- Acid Azelaic acid A dicarboxylic acid sold at 10% as a cosmetic and at 15% and 20% as a drug, which is the whole story of the category.
- Lipid Ceramides One of three lipid classes in the skin barrier, and the one brands name on the front of the box.
- Lipid Cholesterol The barrier lipid with the worst name for marketing and a necessary place in the mixture.
- Lipid Free fatty acids The third barrier lipid class, usually delivered through plant oils rather than named directly.
- Acid Glycolic acid The smallest AHA, which is why it penetrates fastest and stings most.
- Vitamin L-ascorbic acid The best documented vitamin C and the least stable, which is why the packaging matters as much as the percentage.
- Vitamin Niacinamide One of the few actives where the useful range is well documented and the high-percentage versions add little.
- Retinoid Retinaldehyde One conversion step from retinoic acid instead of two, which is the whole argument for using it.
- Retinoid Retinol The retinoid most cosmetic products use, two conversion steps away from the form skin actually responds to.
- Acid Salicylic acid Oil-soluble, which is the single property that decides where it is useful.
- UV filter Titanium dioxide The second mineral filter, usually a supporting act to zinc oxide in a tinted or sheer formula.
- Retinoid Tretinoin The prescription form skin does not have to convert, which is why it is not in any ranking on this site.
- UV filter Zinc oxide The one skincare ingredient whose percentage is always on the box, because the law puts it there.