Retinol, retinoic acid, retinyl esters, retinaldehyde, adapalene, and tazarotene are all retinoids. They are all vitamin A derivatives that share the same benefits. They strengthen the epidermis, prevent the degradation and promote the synthesis of collagen, limit epidermal water loss, and increase cell turnover. Their mechanism of action may vary at the cellular level, but they do the same thing.
For these to be absorbed and to produce effects, they need to be converted into retinoic acid which is their bioactive form– the more steps required to convert them into retinoic acid, the less potent they become.
For example, retinol takes two steps before it is oxidized into retinoic acid. Whereas tretinoin, which is already trans-retinoic, is absorbed right away. This is also why more “retinization” (irritation during the initial phase) can be expected from tretinoin.
Retinoids, that require fewer steps in conversion, are usually prescribed in clinics and given to those with moderate to severe acne, chronically photodamaged skin, excessive keratosis, and scars.
In contrast, retinol is available over the counter because they are much gentler on the skin and have fewer side effects, making them a suitable cosmetic treatment to reduce signs of aging and dyspigmentation.
Dr. Elli Reyes is a specialist of Aesthetic Medicine from the Philippines. With over four years of specialized training, her aesthetic practice has involved a variety of skin treatments involving Botox, fillers, and the like. As a licensed physician, she has been engaged by multiple clinics and is regularly interviewed by the local media as an expert in the science of the skin. Her research and writings to date have centered on nutrition, functional health, and general beauty.