A Complete Comparison of Retinol, Retinal, and Tretinoin: Which is Most Effective for Wrinkles? Differences in Effects and Side Effects - Part 4 of the 'Choosing Truly Necessary Serums Based on Medical Research' Series

It happened while I was checking the ingredient labels.

"Retinol 0.1%"
"High-concentration retinal"
"Pure retinoid formula"

Similar terms are listed, but both the price and concentration vary significantly. On the internet, you may see explanations such as "retinal is 10 times more potent than retinol" or "tretinoin is the strongest."

However,the stronger the ingredient, the less likely it is to be suitable for everyone.

In this article, we will compare the differences between retinol, retinal, and tretinoin, covering not only the strength of their effects but also the volume of clinical research, irritation, and ease of use.

To summarize the conclusion first,

tretinoin has the most extensive clinical track record,

retinol is the easiest to start with as a cosmetic product,

and retinal is expected to be the middle ground between the two.

.

However, there is not yet sufficient large-scale direct comparative research to show that retinal is necessarily superior to retinol.

The difference between the three is the "distance to retinoic acid"

Retinol, retinal, and tretinoin are all vitamin A-relatedretinoids.

The central form that actually acts on receptors in the skin is retinoic acid, which is tretinoin.

The conversion pathway can be organized as follows:

Retinol → Retinal → Retinoic acid

Retinol undergoes a two-step conversion and retinal a one-step conversion to become retinoic acid. Since tretinoin is retinoic acid itself, it does not require conversion within the skin.

Based on this difference, it is generally thought that the strength of the effect increases in the following order:

Retinol < Retinal < Tretinoin

.

However, the actual effect is not determined solely by the conversion stage. It also varies significantly depending on concentration, formulation stability, skin penetration, amount applied, and frequency of use [1].

Retinol—Gentle but with significant product variation

Retinol is the most widely used retinoid in over-the-counter anti-aging cosmetics.

While its action is milder than tretinoin, it has the potential to improve fine lines, uneven skin tone, and skin texture.

In a network meta-analysis published in 2025, 23 randomized controlled trials involving a total of 3,905 people were analyzed. The results showed that topical retinol improved fine lines compared to the control group, and its efficacy for hyperpigmentation was also demonstrated [2].

On the other hand, there are differences between retinol products.

Retinol is unstable when exposed to light and oxygen, and even with the same concentration listed, the amount that reaches the skin varies depending on the container, base, encapsulation technology, and more. Therefore, you cannot compare the strength of products based on concentration numbers alone.

For those using it for the first time or those who want to continue long-term while minimizing irritation, retinol is the most realistic entry point.

Retinal—High expectations, but evidence is still limited

Retinal is also known as retinaldehyde.

Because it is one step closer to retinoic acid than retinol, it may act more efficiently. At the same time, it is difficult to formulate, and its stability against light and oxygen is also a challenge.

In a 2018 randomized, double-blind comparative study, 40 people with photoaging used 0.05% or 0.1% retinal cream for 3 months. Improvements in wrinkles and skin texture were seen at both concentrations, and greater improvement was reported for some evaluation items at 0.1% [3].

Additionally, in a 2021 split-face randomized trial, both a retinal formulation using specific delivery technology and a retinol formulation showed improvements in wrinkle depth and other factors after 8 weeks [4]. However, this was a small-scale study comparing specific formulations, and the results cannot be applied to all commercially available retinal products.

In other words, while retinal is promising, simple conversions such as

it always works faster than retinol
it has the same effect but less irritation
0.1% retinal is equivalent to 1% retinol

cannot be confirmed by current clinical research.

Tretinoin—The most proven, but also the most irritating

Tretinoin is retinoic acid itself and has been studied for many years as the gold standard for treating photoaging.

In a 2024 systematic review, 25 studies comparing tretinoin with other topical treatments were examined. While tretinoin has a wealth of research evidence for improving photoaging signs such as fine lines, hyperpigmentation, and skin texture, there was variability in the quality of comparative studies and evaluation methods [5].

While effects can be expected, in the initial stages of use,

Redness
Dryness
Stinging
Peeling

and similar symptoms are more likely to occur.

Enduring strong irritation while continuing to apply it is not the correct way to enhance its effects. If dermatitis becomes severe, you will not be able to continue, and it may also contribute to post-inflammatory hyperpigmentation.

Tretinoin is not a 'strong serum' but an ingredient to be considered under the premise of a doctor's examination and supervision.

In the end, which one should you choose?

For those using retinoids for the first time

Starting with low-concentration retinol is realistic.

Use it only at night about twice a week, and if there is no redness or dryness, gradually increase the frequency.

For those who find retinol insufficient but do not want to proceed to medical treatment

Retinal is an option.

However, there is no precise conversion of strength compared to retinol. It is important not to use a high concentration every night from the start, but to begin with a low frequency.

For those with clear photoaging who desire more established treatment

There is a way to consult at a dermatology clinic about treatment containing tretinoin.

It is used after confirming not only the strength of the effect but also skin type, the presence of eczema or rosacea, concomitant medications, and UV exposure.

How to start without failing

Use a small amount of retinoid on dry skin after washing your face. If you are worried about irritation,

moisturizer → retinoid → moisturizer

is a method of sandwiching it.

Start with about twice a week, and if redness or stinging persists, reduce the frequency or discontinue use. Be careful around the corners of the eyes, corners of the mouth, and sides of the nose, as these areas are prone to irritation.

Use sunscreen the next morning. It is also safer to avoid starting scrubs, strong peeling agents, or multiple irritating ingredients at the same time.

Furthermore, the European Medicines Agency, as a precautionary measure, recommends that those who are pregnant or planning a pregnancy should not use topical retinoids [6].

Choosing 'Sustainability' Over 'Maximum Strength'

Comparing the three, tretinoin leads in terms of medical track record.

However, in actual skincare, the ingredient with the strongest effect is not always the best.

It is more rational to consistently use a low-concentration retinol than to use a high-concentration product that causes dermatitis and leads to immediate discontinuation.

The difference between retinol, retinal, and tretinoin is not a simple ranking of strength.

Choose an ingredient that suits your goals within a range that your skin can consistently tolerate.

That is the most important answer for utilizing retinoids in anti-aging care.

Next time (Part 5), we will enter Part 2, where we verify the effectiveness of popular ingredients.

Does niacinamide really work for pores, dark spots, and wrinkles? We will organize the concentrations where effects can be expected and the limitations that are often difficult to understand from advertisements.

Click here for Part 5 ☟.

Click here for past articles from parts 1-3 of the serum series based on medical research! ☟

References

[1] Milosheska D, Roškar R. Use of retinoids in topical antiaging treatments: A focused review of clinical evidence for conventional and nanoformulations. Advances in Therapy. 2022;39(12):5351-5375. doi:10.1007/s12325-022-02319-7.

[2] Lin L, Chen X, Liu C, Wang Q, Lian W, Xu X, et al. Comparative efficacy of topical interventions for facial photoaging: A network meta-analysis. Scientific Reports. 2025;15:26889. doi:10.1038/s41598-025-12597-0.

[3] Kwon HS, Lee JH, Kim GM, Bae JM. Efficacy and safety of retinaldehyde 0.1% and 0.05% creams used to treat photoaged skin: A randomized double-blind controlled trial. Journal of Cosmetic Dermatology. 2018;17(3):471-476. doi:10.1111/jocd.12551.

[4] Lee CM, Maibach HI. The efficacy and safety of multilamellar vesicle containing retinaldehyde: A double-blinded, randomized, split-face controlled study. Journal of Cosmetic Dermatology. 2021;20(10):3318-3326. doi:10.1111/jocd.13993.

[5] Siddiqui Z, Zufall A, Nash M, Rao D, Hirani R, Russo M. Comparing tretinoin to other topical therapies in the treatment of skin photoaging: A systematic review. American Journal of Clinical Dermatology. 2024;25(6):873-890. doi:10.1007/s40257-024-00893-w.

[6] European Medicines Agency. Retinoid-containing medicinal products: Updated measures for pregnancy prevention during retinoid use. European Medicines Agency.