Retinol is a derivative of vitamin A that promotes cell turnover, fights acne, diminishes signs of aging, firms skin, and provides all the benefits of an antioxidant. While its advantages are many, there are two points of caution: retinol can increase sun sensitivity, and any product that contains this ingredient is not safe for those trying to conceive or those who are pregnant or breastfeeding. It is available in both cosmetic skincare products and prescription formulas such as Differin, Tazorac, and Tretinoin.