María Monterrubio

Do you have any doubts about the potential advantages & disadvantages of using topical products with retinol or other retinoids in the summer? Get clarity on that: learn how retinoids work in your skin, why they can be incredibly beneficial (especially when the sun is brighter), and in what cases you might need to think twice before introducing them in your routine.

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Last updated: September 12, 2022

Hi everyone! Let’s get clear about how retinoids can help your skin, whether summer (when the sunlight is more intense and prolonged) or wintertime.

What are retinoids?

Retinoids are biological compounds that include vitamin A1 (retinol) and its natural and synthetic derivatives. In adults, they are essential to maintain epithelial homeostasis, that is, to keep your epithelial tissues (including the skin or intestinal lining) working as they should.

They also orchestrate embryonic development: that’s why they should not be taken orally or even applied on your skin if you are pregnant or breastfeeding – the last thing you want is to mess up with your baby’s growth –.

Some retinoids can degrade upon light exposure due to their molecular structure (which features a long hydrocarbon chain with alternating double bonds that endows them with a yellowish or orangish color). Thus, applying them to your skin in the morning might reduce their effectiveness. That is the reason why it is way better to use them at night. 

That is also why not all retinoid-based skincare products are equally effective. Some retinoids, like retinol, need to be stabilized. Also, the quality and purity of the retinoid molecules included in the formulations yield differences in terms of efficacy.

What’s the difference between retinol, retinaldehyde, and retinoic acid?

The difference among these three natural retinoids is mainly their strength. Whenever topically applied or orally ingested (for example, after eating vitamin A-rich foods), vitamin A, or retinol, has to be converted into retinoic acid. Otherwise, it does not work: the biologically active form of retinol is all-trans retinoic acid (also called tretinoin). 

All-trans-retinol conversion (all-trans refers to the molecular conformation in which the retinol molecule must be) into all-trans-retinoic acid happens within our skin cells in two steps (mediated by two different enzymes):

· First, retinol has to convert into retinaldehyde; this is a rate-limiting, highly regulated step.

· Then retinaldehyde (retinal) can turn into retinoic acid, the active form of retinol.

Therefore, all that needs to occur in your skin before retinol can do anything for it. Retinaldehyde (retinal) gets converted into retinoic acid only in one step (not two); it is slightly more potent than retinol.

However, retinoic acid works right away after its application. You can achieve similar effects on your skin with the consistent, topical use of retinol and retinoic acid. Only it will take quite longer to get the same visible results with retinol.

How do retinoids benefit your skin, especially in the brighter months?

Most people can tolerate and benefit from topical retinoids, even people with sensitive skin or, for instance, rosacea. It’s all a matter of knowing how to incorporate them into your routine.

If you apply quality retinoids consistently and appropriately to your skin, they will prevent and treat cutaneous photodamage. That’s why their use is relevant all year long, even more, when there is more intense sunlight. 

Retinoids won’t make your skin more sensitive to the sun or more prone to burn. We know that they do not decrease the Minimal Erythema Dose (the amount of ultraviolet radiation required to redden your skin).

That said, regardless of retinoids usage, you should always keep practicing the number one rule of great skin, which is sun protection. If you leave your skin unprotected, ultraviolet light will ruin it during the day. In that case, it does not matter what on you put on your skin at night.

What exactly do retinoids do within your skin to prevent & correct photodamage?

Retinoic acid (and its synthetic analogs) within skin cells act through the binding of specific receptors, called retinoid receptors.

Once this happens, those complexes of retinoic acid and retinoid receptors can bind concrete gene sequences. And that results in the regulation of the expression of those genes. That is the activation or inhibition of the synthesis of the proteins encoded by them.

Retinoids increase cell renewal in the epidermis and collagen in the dermis

On the one hand, when retinoic acid binds sets of genes with sequences known as RAREs (Retinoic Acid Response Elements), it activates the synthesis of the proteins encoded by those genes.

Through this mechanism, retinoic acid promotes the expression of proteins involved in the growth and differentiation of the cells that comprise the epidermis (called keratinocytes).

There are several layers of keratinocytes in the epidermis (see the image below). In the bottom layers are the most proliferative keratinocytes (which grow). Some of those eventually cease to grow so fast and at that moment begin the process of differentiation. Differentiating keratinocytes migrate up and successively become part of distinct upper (less proliferative) epidermal layers.

At the uppermost skin layers, differentiating keratinocytes die. And give rise to what we know as the stratum corneum or protective barrier (which is the most external cutaneous layer, made up of dead keratinocytes and lipids that slough off continuously).

Vitamin A (among other molecules) tightly regulates the whole process of epidermal proliferation and differentiation.

The cutaneous tissue image below shows what happens in our skin upon treatment with all-trans retinoic acid (the biologically active form of vitamin A). It stimulates keratinocyte proliferation in the basal layer. And a very tidy process of differentiation. All that results in increased epidermal thickness and a more organized epidermis.

As you can see in the image, even the stratum corneum (the most external skin layer, depicted with number 2) gets more dense and compact.

Retinoids also have a positive impact on the dermis. That is due to the ability of retinoic acid to enhance collagen production (and dermal thickness).

Retinoids inhibit non-beneficial stress and inflammatory responses

On the other hand, through the binding of response elements other than RAREs in different genes, retinoic acid can repress their expression.

Throughout that mechanism, retinoids impede the expression of proteins that bring about photoaging (aging of the skin caused by sunlight) and pre-cancerous features. 

Often, those proteins are mediators of inflammation. And the repression of those by retinoic acid avoids harmful inflammatory states and stimulates the well-functioning of the cutaneous immune system.

In the epidermis, that evades the over-activation of keratinocytes and melanocytes (the cells that produce melanin). And, therefore, lowers the occurrence of skin cancers and melanin production disorders (which cause skin discolorations, such as dark spots). Topical retinoids reduce the incidence of actinic keratosis, which are pre-cancerous lesions that, if left alone, can eventually become non-melanoma skin cancers (specifically, squamous cell carcinomas).

And in the dermis, that inhibits the activation of matrix metalloproteinases upon sun exposure. Matrix metalloproteinases are enzymes that get activated even after just a few minutes of exposure to sunlight and break collagen and other extracellular matrix components in the dermis, causing wrinkles, photoaging, and a worse skin barrier.

Those are some of the various ways through which retinoids limit cutaneous sun damage. So, now you know why they are such a gem to dermatologists! 😉

When do you need to think twice before using topical retinoids in the summer?

You might want to reconsider topical retinoids right now (in the summer) if you have never used retinoids before.

Why? Because when you start a topical retinoid (including retinol), as expected, you might experience some accelerated skin desquamation. Remember that retinoids increase epidermal renewal. Until the skin gets used to retinol or other retinoids, you might notice some extra peeling.

That might temporarily correlate with a mildly compromised skin barrier that needs extra care (in the form of added moisturization and sunscreen). And it might not be that easy to manage if you have never experienced that.

If you would like to start a retinoid now anyways (and not wait until October or November), stay tuned! Soon I will explain how to introduce a retinoid into your skincare routine safely and effectively on this blog. Along with some skincare product recommendations on that stage.

Thanks for reading my posts. 🙂 Please leave any thoughts or questions in the comments section below.

Enjoy the rest of the summer!

Love,

María

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