Retinaldehyde: Skin benefits of retinoids with less irritation

Retinoinds, such as retinoic acid (a.k.a. tretinoin, Retin-A), are a group of biochemical agents clinically proven to reduce fine lines, wrinkles and other signs of skin aging. Unfortunately, retinoids can be irritating in sensitive individuals and if used improperly may do more harm than good. (See our article about retinoids). One alternative is to use less irritating precursors, the substances that are themselves inactive but can be converted to active (directly-acting) retinoids by the body. The most common retinoid precursor in skin care are retinol and retinyl palmitate, both forms of vitamin A. (In fact, retinyl palmitate is a biological storage form of retinol in the body). Unfortunately, while less irritating, retinol and retinyl palmitate tend to be considerably less effective than retinoic acid and other directly acting retinoids. The main reason is that they need to undergo at least two conversion steps before becoming retinoic acid. Such conversion tends to be slow and its rate varies among individuals. As a result, anti-aging effects of retinol and retinyl palmitate tend to be more modest and less reliable than those of retinoic acid and analogous retinoids (see our article retinol / retinyl palmitate).

Fortunately, there is a less common retinoid precursor that is just one step away from retinoic acid. Its name is retinaldehyde (a.k.a. retinal) and it is also considered a form of vitamin A. In just one step, the body can convert retinaldehyde either to retinoic acid or to retinol (which can be further converted to retinyl palmitate). Due to such metabolic dynamics, treating the skin with retinaldehyde could produce therapeutic levels of retinoic acid while reducing the risk of side effects associated with retinoid excess.

So, does retinaldehyde indeed combine the effectiveness of directly acting retinoids with lower potential for skin irritation? The existing research is limited but appears to point is that direction. A German study by Dr. Fluhr and co-workers published in the journal Dermatology in 1999 compared irritation potential of retinol, retinaldehyde and retinoic acid and concluded that both retinol and retinaldehyde had a good tolerance profile compared to retinoic acid. A French study by Dr Boisnic and co-workers (also published in the journal Dermatology in 1999) looked at the ability of retinaldehyde to reverse skin damage induced by UVA radiation. The researchers concluded that retinaldehyde exhibited "many of the properties of tretinoin [trans-retinoic acid] in its biological and beneficial effects on photoaging" and in particular improved dermal connective tissue by boosting "repair of elastic fibers and reversing collagen alteration induced by UVA exposure". However, more studies are needed to assess the full scope of skin rejuvenation benefits of retinaldehyde. Particularly useful would be those directly comparing retinaldehyde with retinoic acid and/or other retinoids over reasonably long periods of realistic topical application. Only such studies can fully answer the question whether retinaldehyde can provide comparable or superior anti-aging benefits compared to active retinoids. However, for people with sensitive skin or those intolerant of retinoids, topical retinaldehyde may be worth a try even before such data is available. Unfortunately, optimal concentrations and usage practices for topical retinaldehyde need further research. Most studies conducted so far used topical retinaldehyde in concentrations 0.05% and 0.1%.

In addition to skin rejuvenation, there is another application where retinaldehyde may prove comparable or even superior to retinoids - treatment of acne. Retinoids, such as retinoic acid (tretinoin, Retin-A) and adapalene (Differin), have been one of the established acne treatments for decades. Obviously, considering that retinaldehyde is converted to retinoic acid in the body it could conceivably have the same effect on acne as directly acting retinoids. Furthermore, since it is less irritating than retinoids, retinaldehyde may be easier to combine with other potentially irritating acne treatments, such as alpha-hydroxy acids, beta-hydroxy acids or benzoyl peroxide. In fact, two studies have demonstrated the effectiveness of topical 0.1% retinaldehyde combined with 6% glycolic acid in treating acne. Also, there is evidence that retinaldehyde possesses some antimicrobial activity against P. acnes, the bacteria involved in the development of acne. In fact, Dr Pechere an co-workers from Geneva University Hospital, Geneva, Switzerland showed that retinaldehyde is a much stronger antibacterial that either retinol or retinoic acid (published in the journal Dermatology in 2002). It would be useful to conduct studies directly comparing retinaldehyde with retinoic acid and other directly acting retinoids as an acne treatment. The research so far indicates that retinaldehyde holds considerable promise as an acne treatment, especially in combination with other anti-acne agents.

A few commercial skin care products with retinaldehyde are available (albeit not inexpensive) and, as opposed to directly acting retinoid creams, do not require a prescription. If you decide to shop for a topical retinaldehyde product, make sure to check for proper concentration. As we mentioned, the clinically studied retinaldehyde concentrations were typically 0.05% - 0.1%. While less irritating than directly acting retinoids, retinaldehyde can still cause skin irritation and/or excessive dryness in sensitive individuals. It may be prudent to start with lower concentrations (e.g. by diluting with inert vehicle) and/or apply less frequently (e.g. every other day) and then gradually increase the concentration/frequency to the desired level. If even cautious use of retinaldehyde is too irritating for you, consider switching to (retinol / retinyl palmitate).

Finally, I should mention a possible new alternative to retinaldehyde and other retinoid precursors: retinyl retinoate. Just like retinaldehyde, retinyl retinoate is just one metabolic step away from retinoic acid and is reportedly at least as effective. It is also reported to have a favorable side effects profile and greater stability than most other retinoid precursors, especially when exposed to sunlight. Unfortunately, being a novel agent, retinyl retinoate is only minimally researched and may not be ready from prime time just yet. (See our retinyl retinoate acticle for details.)

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