Retinol is a weaker, over the counter version of tretinoin, a prescription vitamin A derivative that is highly effective in reversing sun damage and signs of aging. Tretinoin decreases fine lines, evens skin color, improves texture, tightens pores, and stimulates blood flow and collagen production. However, quite a few people cannot tolerate tretinoin because it can be highly irritating and drying. Retinol is milder; while the results may not be as dramatic, more people tolerate it well. Like tretinoin, retinol encourages skin cell turnover; this new skin is delicate and should not be exposed to the sun. That is why these ingredients should only be found in products intended for night use.
Vitamin A derivatives, including retinol, rapidly break down when exposed to the sun and air. That’s why retinol-containing products should always come in pumps or tubes with tight-fitting caps. Once opened, these products do not keep well and should be used within a couple of months.