What’s the difference?(Retinoic Acid, Retinaldehyde, Retinol & Retinol Esters)
No matter which retinoid you choose, your skin can only use the active form of vitamin A, retinoic acid.
Retinoic acid binds to the retinoid receptors in our bodies, where it normalizes cellular renewal and cellular repair processes. This is how retinoids work their magic on lines, dark spots and more!
One step: Retinaldehyde is the direct precursor to retinoic acid.
Two steps: Retinol first converts to retinaldehyde, and then from retinaldehyde into retinoic acid.
Three steps: Retinol esters convert to retinol, then from retinol to retinaldehyde, and finally from retinaldehyde to retinoic acid.
The closer the compound to retinoic acid, the more readily it converts—and the more effective it becomes.
But keep in mind that the conversion rate can also vary depending on the individual (some people convert retinoids into retinoid acid more quickly than others!). Other factors include the concentration of the active ingredient and whether or not it has degraded (some retinoids are unstable).
Retinol esters are the mildest types of retinoids, because they need to be converted three times within our skin before they become active. This makes them a good choice for sensitive, reactive skin and anyone new to retinoids, as they are unlikely to cause any irritation.
But not all retinol esters are made equal. The most effective is retinyl propionate, which has been shown in higher concentrations to reduce wrinkles and pigmentation. Retinyl palmitate is your next best choice, with some benefits for sun damage and skin thickening.
The other retinol esters—retinyl acetate and retinyl linoleate—are weaker and best used in combination with each other and/or stronger retinoids.
Retinol, the most popular over-the-counter retinoid, goes through two conversions before it becomes active. That means you're getting a more effective form of vitamin A than the retinol esters. In fact, retinol has been proven to induce similar skin changes as retinoic acid—it may just take a little longer to get there. Compared to retinoic acid, retinol is about 20 times less potent.
Research shows that retinol can significantly improve wrinkles, whether caused by sun damage or normal ageing. It can also help to fade pigmentation, improve skin elasticity and smooth rough skin texture.
The downside is that retinol can be drying and irritating for some people, although not as much as stronger retinoids like tretinoin.
However, even sensitive skin can be trained to tolerate retinol, also keep in mind that the inactive ingredients in a formula often trigger irritation, not necessarily the retinol itself.
Retinaldehyde, also known as retinal, is directly converted into retinoic acid by our skin. It converts to retinoic acid 11 times faster than retinol, and is said to be approximately 20 times more potent than retinol. (We just don't have as much research behind it yet.) As such, retinaldehyde can produce skin changes that are comparable to retinoic acid.
For example, retinaldehyde was proven to be just as effective as retinoic acid for treating sun damage, with fewer side effects. Other studies have shown that it improves skin thickness and elasticity, repairs UVA damage and (in conjunction with hyaluronic acid) reduces wrinkles, nasolabial folds and crow's feet. Retinaldehyde is also particularly effective for acne, since it is antibacterial and helps regulate cell turnover.
Similar to retinol, you can get some dryness and irritation from using retinaldehyde, but not on the same level as you would from a pure retinoic acid.
In the end, the regular use of retinoids can give you improvements such as fewer fine lines and wrinkles, firmer skin, more even skin tone. Dermatologists often refer to retinol as the "gold standard" anti-ageing ingredient because it is widely available and has decades of research demonstrating its effectiveness.