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The Dermatologist's Guide to the
Use of retinoic acid (tretinoin)
and other retinoids for
Skin Renewal and Anti-Aging Skin Care:
How retinoids help reduce the visible signs of skin aging
Retinoids are a category of skin care ingredients that are derivatives of vitamin A.
Retinoids have been in use for decades, and are widely used in the treatment of mild to moderate acne.
They are also used to reduce the visible signs of skin aging.
For my patients seeking effective skin renewal skin care products, I recommend products with retinoids most often.
There are both natural and synthetic retinoids.
They may be found in either prescription medications or over-the-counter products.
Ingredients used in prescription medications include retinoic acid (also known as tretinoin), adapalene, and tazarotene.
Retinoid ingredients used in over-the-counter products include retinol, retinaldehyde, and retinyl esters.
Although they can be irritating, most people can still use products with retinoids. It's really important to make sure that you're using them the correct way, and it's equally important to find a formulation that works for your skin.
For patients with less sensitive skin who can handle the potential irritation, the prescription retinoids are considered the most effective.
For those with more sensitive skin, I usually recommend products with either retinol or retinaldehyde.
We have a large body of literature on retinoids, mainly focused on studies of the prescription ingredient retinoic acid. This compound has shown effectiveness, over decades, in the treatment of acne. It has also been studied and shown effective in reducing multiple signs of skin aging. As just one example, strong clinical trials have shown that it helps improve the appearance of fine lines and wrinkles. Research has shown that it also helps to even out skin tone, enhance cell turnover, and improve collagen production.
If you'd like to read about the biochemical mechanism of action of retinoids, as well as a review of the many clinical research trials performed on retinoids, this medical journal article provides a great review.
Retinoids in the Treatment of Skin Aging
Retinoic acid is one of the most studied, and most effective, compounds for treating the visible signs of skin aging, including fine lines and wrinkles, skin roughness, and dark spots.
While there are fewer studies for the retinoid ingredients found in OTC products, these have also shown promising results. The most promising ingredient is adapalene, an ingredient that used to be available only by prescription, but that is now available in both a prescription (higher concentration) and an OTC (lower concentration) formulation. Other promising OTC retinoid ingredients include retinol and retinaldehyde. These other ingredients aren't as effective as the prescription ingredients, but they're a lot less irritating for most people.
Retinoic acid improves many of the visible signs of skin aging. It does this by improving fine lines and wrinkles, reducing surface roughness, increasing skin collagen production, and helping to even out skin tone by reducing the appearance of dark spots.
Improves the Appearance of Fine Lines and Wrinkles
Promotes epidermal cell turnover by binding to retinoic acid receptors. This activates certain genes that are involved in cellular proliferation and differentiation, which helps dead skin cells slough off from the surface of the skin more effectively.
Increases the capacity of the epidermis to hold water through stimulation of glycosaminoglycan synthesis
Also stimulates collagen synthesis through increases in procollagen
Also prevents further breakdown of the dermal matrix by inhibiting the enzymes that break down collagen
Evens out Skin Tone
Enhances epidermal cell turnover.
This helps reduce the amount of contact between keratinocytes (skin cells) and melanocytes (pigment-producing cells).
Reduces Skin Roughness
Promotes epidermal cell turnover
Helps dead skin cells slough off from the surface of the skin more effectively
Different Types of Retinoids: Retinoic Acid, Retinol, Retinaldehyde
Retinoic acid is the biologically active form of vitamin A.
If you use retinol and retinaldehyde in a skin care product, they are absorbed into the skin. They are then converted into retinoic acid.
Retinol is oxidized into retinaldehyde in the skin. Retinaldehyde is oxidized into retinoic acid.
Retinol and retinaldehyde can produce significant improvement in the appearance of fine and deep wrinkles
In one clinical study, researchers reported that retinaldehyde was effective and well tolerated in patients with photodamage (skin damage due to years of UV exposure). "At week 18, a significant reduction of the wrinkle and roughness features was observed with both retinaldehyde and retinoic acid."
In studies, the use of topical retinol has also resulted in significant improvement in reducing the visible signs of skin aging.
For example, this study used a split-face treatment and compared the use of retinol cream (on one side of the face) to tretinoin cream (on the other side of the face). After 12 weeks, they showed significant improvement in multiple signs of aging skin, including overall sun damage, fine lines and wrinkles, coarse lines and wrinkles, "skin tone brightness", skin pigmentation, and rough skin. In this study, they actually found equivalent results between the use the retinol cream and a comparable dose of tretinoin cream.
Retinyl esters such as retinyl propionate and retinyl palmitate are not as effective for reducing the visible signs of skin aging
Retinyl esters include derivatives of retinol such as retinyl acetate, retinyl propionate, and retinyl palmitate. These have been widely used in cosmetic products, but I don't typically recommend them, since we have limited evidence that they're effective. They were first studied because of animal studies: retinyl propionate was able to promote collagen formation in mice exposed to UV radiation. However, results from a double-blind, placebo-controlled trial were not promising. In this study, volunteers used either a topical retinyl propionate cream or placebo for almost a year (48 weeks). At the end, researchers could not demonstrate any statistically significant difference between the active cream or the placebo cream, either in clinical visible features or in skin biopsy changes.
Here are some links to before and after photos of patients who have used topical retinoids in clinical studies:
Treatment of post-inflammatory hyperpigmentation due to acne in African-American women, before and after 40 weeks of treatment with tretinoin
Treatment of fine wrinkling before and after 24 weeks of treatment with retinol
Treatment of fine lines and wrinkles, before and after 12 weeks of treatment with retinol
Bakuchiol: Further Research Needed On This "Natural Retinol Alternative", But Promising Preliminary Results
One natural compound that I'm interested in is a substance called bakuchiol. This compound is NOT a retinoid, but it seems to have several of the same impacts in the skin. That's why it is sometimes referred to as a "natural retinol alternative."
Bakuchiol is a phytochemical, found mainly in the seeds of a plant from India called babchi. Bakuchiol and retinol have different chemical structures, but they seem to work in the skin in similar ways. Laboratory studies suggest that both compounds affect genes in our skin cells that impact retinoic acid receptors. Studies also suggest that both act to increase certain enzymes that promote collagen synthesis. Bakuchiol has also demonstrated some impressive antioxidant effects.
In one randomized, placebo-controlled, double-blind study, 44 patients were asked to apply either bakuchiol 0.5% cream twice a day or retinol 0.5% cream twice a day to their face. High resolution photographs were taken before, during, and after treatment, and dermatologists assessed the patients for redness and pigmentation. Neither the patients nor the researchers knew which group was using which product.
After using the products for 12 weeks, both groups were found to have a significant decrease in wrinkle surface area and hyperpigmentation (dark marks). In terms of side effects, the bakuchiol group did well with the treatment, while the retinol users reported that they had more flaking and stinging on their face.
Since this is a small study, we definitely need more research to understand more about the potential side effects, the potential benefits, and if certain people might react to this ingredient differently. It is intriguing preliminary research, though, and I'm watching out for more studies on this interesting substance.