Retinoids are part of the Vitamin A family. They're well-known for their incredible benefits to our skin, making them a powerful tool in fighting aging, acne, and hyperpigmentation.
Did you know that retinoids also play a crucial role in many of our body's essential functions? From maintaining healthy vision to supporting embryonic development, retinoids truly are remarkable.
When taken orally, tretinoin, a type of retinoid, has been shown to be effective in treating leukemia. This is due to retinoids' remarkable ability to regulate cell growth cycles. So, not only do retinoids work wonders on our skin, but they're also vital for our overall health.
When it comes to skincare, tretinoin was the first retinoid to be approved by the FDA in 1971 for treating acne. You might know it by its brand name, Retin-A.
Here's an interesting tidbit: when people started using topical tretinoin for their acne, they began to notice improvements in their overall skin condition. This led to further research, and in 1995, the FDA approved tretinoin for treating sun-damaged, prematurely-aged skin.
Some other popular topical skincare retinoids you might be familiar with include retinol and retinaldehyde, often called retinal with an "A." For those dealing with acne, you may have come across isotretinoin (Accutane), adapalene (Differin), and tazarotene (Tazorac).
In this discussion, we'll be focusing on the popular anti-aging and anti-acne topical retinoids, specifically retinol, retinal, and tretinoin. Keep in mind that the terms retinoic acid and tretinoin can be used interchangeably.
What Can Retinoids Do for My Skin? And How Do They Work Exactly?
Retinoids have been proven to help keep your skin healthier, which is why dermatologists are such big fans of them. Let's dive deeper into how retinoids work, step by step.
When applied and absorbed into the skin, retinol and retinal need to be converted into retinoic acid. Retinol first gets converted into retinal, and then retinal gets converted into retinoic acid. So, retinol is two steps removed from retinoic acid, while retinal is just one step away. Enzymes drive both of these conversion processes.
Enzymes play a crucial role in determining whether a retinoid is actually beneficial for the skin. For instance, when ingested, beta-carotene (in carrots, for example) is converted into retinal by enzymes present in the cells of the gut lining. However, these enzymes are not present in skin cells — that's why you can't just rub carrot juice on your skin and expect any benefits.
Once retinol or retinal is converted into retinoic acid, it activates skin cells to power the regeneration cycle. Here's the sequence:
Retinoids Can Plump Up the Skin by Empowering Skin Cell Regeneration
Retinoids work to plump up the skin by boosting the c-Jun transcription factor, which is essential for the proper division and proliferation of cells. By upregulating the c-Jun transcription factor, retinoids directly stimulate an increase in the number of epidermal skin cells, resulting in a thicker epidermis layer (Saurat et al. 1994, Kafi et al. 2007, Kong et al. 2015, Shao et al. 2017).
Cell proliferation means the division of a cell into two new cells — a fancy way of describing the creation of more cells. Transcription factors are proteins that activate specific parts of your DNA to produce more of certain proteins, setting off a chain of signals leading to increased cell proliferation.
Think of your skin as having two primary layers: the epidermis and the dermis. The epidermis is the outer layer that protects your body. It contains melanocytes that produce melanin (protecting you from UV rays), as well as immune cells called Langerhans cells that help guard against infection. Consider the epidermis as your first line of defense against the environment. As you age, the epidermis thins, becoming fragile and more prone to damage — meaning the defenses weaken.
Here's a figure from a 2015 study by Kong and colleagues that illustrates the effects of retinoids on the skin.
When a topical retinoid, even a relatively mild 0.1% retinol, is applied, you can see a noticeable increase in epidermal skin thickness, represented by the blue staining. Thicker epidermis means a stronger defense against environmental factors like allergens, bacteria, microbes, and UV damage.
Additionally, you can observe an increase in procollagen, a precursor to collagen, shown as red staining in the layer underneath the epidermis.
This is the dermis — the inner layer that contains blood vessels providing nutrients for the skin, as well as sweat and oil glands and hair follicle roots. Crucially, the dermis also contains proteins like collagen and elastin which provide structure and support to your skin, giving it a youthful bounce.
In general, more procollagen means more collagen. We'll get back to collagen shortly — but first, let's talk about the blood vessels in the dermis.
Retinoids Can Improve Blood Flow to the Skin
Another positive result of retinoid-driven skin rejuvenation is the increased proliferation of endothelial cells — the cells that form the lining of blood vessels, helping to support healthy skin.
In this figure, taken from a study by Shao and colleagues, you can observe that applying a topical retinoid for just a week resulted in the proliferation of endothelial cells in the dermis. Enhanced blood flow to the skin leads to better nutrient delivery, as well as improved skin color and tone.
Retinoids Boost Collagen and Elastin in the Skin
Retinoids work wonders for boosting collagen and other essential structural proteins, like elastin, in the dermis. Think of collagen as the scaffolding that supports your skin, preventing it from sagging. Elastin, on the other hand, is like the lycra in your leggings — giving your skin bounce and elasticity.
We have a whole article on the science of collagen. Read the Deep Guide to Collagen here.
By enhancing the collagen and elastin content in your skin, retinoids can help reduce wrinkles in both aged and sun-damaged skin. A study by Shao and colleagues revealed that applying a topical retinoid for just one week could significantly increase procollagen production — by three times compared to a placebo.
The same study also found that retinoid application led to a fourfold increase in elastin, as shown by the red stain. These increases in collagen and elastin directly contribute to smoother, less wrinkled, and more bouncy skin.
Retinoids Can Treat Acne — And Retinal Has a Unique Antibacterial Power
Retinoids tackle acne through two main approaches.
Interestingly, retinaldehyde — retinal with an "A" — possesses antibacterial properties, which is a unique feature among the retinoid family. Retinal's special chemical structure makes it highly reactive, providing it with potent antibacterial properties. For those who enjoy technical details: retinal's reactivity is due to the presence of an aldehyde group in the isoprenoic lateral chain of its molecular structure.
A study by Pechere and colleagues provides evidence that retinal is effective against acne. The researchers compared the performance of 0.05% retinal and 0.05% retinoic acid in combating bacteria — a head-to-head analysis of their antibacterial capabilities.
The study showed that 0.05% retinal treatment for 2 weeks led to a decrease in the density of acne-causing bacteria (P. acnes). On the contrary, 0.05% tretinoin had no effect on reducing P. acnes density.
If addressing acne is a key concern, using retinal is a no-brainer. Unlike tretinoin, retinal's aldehyde structure gives it direct antibacterial action against the bacteria responsible for breakouts.
Retinoids Can Also Help with Hyperpigmentation
Retinoids have even more benefits for your skin — they can help improve hyperpigmentation through several different mechanisms. We'll briefly go over these mechanisms now.
Treating hyperpigmentation is generally more effective when retinoids are used in combination with other ingredients, as different ingredients can work together in complementary ways (Leydon et al. 2017, Zasada and Budzisz 2019). Combining retinoids with hydroquinone can diminish hyperpigmentation even more effectively, as can retinoid-glycolic acid, retinoid-arbutin, and retinoid-vitamin C combinations (Mukherjee et al. 2006, Boswell 2006).
Check out our Deep Guide to Hyperpigmentation for a more in-depth discussion of treatment approaches.
Conclusion
To summarize, retinoids are one of the best and most effective anti-aging ingredients that additionally can help fight acne and hyperpigmentation.
All retinoids should be avoided during pregnancy and lactation. Check out our article on pregnancy and skincare for more information. And always wear sunscreen when using retinoids, particularly in the first few weeks, as this is when retinoids increase sun sensitivity.
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