All About Retinoids from A to Z: Mechanism of Action, Evidence, and Selection
Category: Ingredients
Summary: Retinol, retinal, retinyl esters, HPR, and prescription retinoids: how to distinguish them by nomenclature, what happens to them in the skin, and why the percentage on the label does not always indicate efficacy. We examine the mechanisms of action, real clinical studies only, tolerability, and product selection.
Why retinoids cannot be compared by percentages alone
One product’s label says Retinol 0.3%, another says Retinal 0.1%, and a third promises 10% Granactive Retinoid. At first glance, it seems fairly simple to compare them: the higher the percentage, the stronger the product. But with retinoids, that logic does not work.
Under the umbrella term “retinoids,” an entire group of compounds related to vitamin A is combined. They differ in chemical structure, stability, ability to penetrate the skin, mechanisms of action, and the amount of clinical research supporting their efficacy.
Retinol must undergo several stages of conversion in the skin before its main active metabolite, retinoic acid, is formed. Retinal is one step closer to it. Tretinoin is retinoic acid itself. And HPR, or hydroxypinacolone retinoate, belongs to a separate group of compounds for which a different mechanism of action is proposed.
This is precisely why the same concentration of different retinoids does not mean the same biological activity. Moreover, even two products with the same retinoid and the same percentage can differ noticeably in efficacy and tolerability. The base of the formula, stabilization, packaging, and release rate all matter.
The main task when choosing a retinoid is not to find the highest percentage, but to choose a compound with an appropriate evidence base, a workable formula, and tolerability acceptable for the skin.
Let us sort this out step by step: first the nomenclature, then the behavior of retinoids within the skin, and finally how well the effect of topical retinoids is supported by clinical research.
1. Main types of retinoids and their INCI
INCI is the International Nomenclature of Cosmetic Ingredients. It is by this that one can determine which substance the manufacturer has included in the formula. However, INCI itself does not reveal the exact concentration, the quality of the raw material, or the amount of the substance that will remain in the product by the end of its shelf life.
| Retinoid | INCI | Characteristics |
|---|---|---|
| Retinol | RETINOL | One of the most studied cosmetic retinoids. Must be converted to retinal, then to retinoic acid |
| Retinal | RETINAL, sometimes RETINALDEHYDE | The immediate precursor of retinoic acid |
| Retinyl esters | RETINYL PALMITATE, RETINYL ACETATE, RETINYL PROPIONATE, RETINYL LINOLEATE | Require additional conversion steps; evidence for the efficacy of individual esters is limited |
| HPR | HYDROXYPINACOLONE RETINOATE | A retinoic acid ester for which a mechanism of interaction with RAR receptors is claimed; clinical data are substantially fewer |
| Tretinoin | TRETINOIN | Retinoic acid, used in medicinal products |
| Adapalene | ADAPALENE | A synthetic retinoid-like agent, used primarily for acne |
| Tazarotene | TAZAROTENE | A prescription retinoid, in particular for the treatment of acne and certain other dermatological conditions |
| Trifarotene | TRIFAROTENE | A prescription retinoid used for acne |
Concentrations of 0.1%, 0.3%, 0.5%, and 1% are frequently encountered in studies and commercial products with retinol. For retinal, the popular concentrations of 0.05% and 0.1% have been studied. But these are merely examples, not a universal scale by which the strength of any cosmetic product can be calculated.
Furthermore, one cannot automatically apply to cosmetic retinoids the same logic as to medicinal ones. For example, adapalene does not undergo the classic chain of conversion from retinol to retinoic acid. Therefore, it is incorrect to simply place it on the same linear scale next to retinol and retinal.
Retinol: the most studied cosmetic option
INCI: RETINOL
Retinol is widely used in cosmetics aimed at improving the signs of photoaged skin. It has been studied in the context of fine lines, uneven texture, uneven tone, and changes in epidermal structure.
Why is it so popular? On the one hand, retinol is capable of influencing cellular processes related to skin renewal and remodeling. On the other hand, it requires two successive conversions for retinoic acid to be formed. This allows the skin to regulate the metabolism of the substance, which minimizes the risk, although it does not guarantee a complete absence of irritation.
Retinol also has a significant drawback: it is sensitive to oxygen, light, and storage conditions. Simply put, it is unstable. Therefore, the percentage on the packaging does not tell the whole story. If the substance gradually degrades in a poorly designed formula, its actual amount and biological activity will decrease. This is precisely why many brands place particular emphasis on the stability of their retinol-containing products.
An intermediate conclusion: evidence for the efficacy of retinol itself and evidence for the efficacy of each specific cosmetic product are not the same thing. Even a well-studied ingredient does not guarantee the same result in any formula.
Retinal: one step away from retinoic acid
INCI: RETINAL, RETINALDEHYDE
Retinal, or retinaldehyde, is an intermediate product between retinol and retinoic acid. In the classic metabolic pathway, it requires only one subsequent oxidation step for retinoic acid to be formed.
Hence the widespread claim that retinal is stronger than retinol. It does indeed have a biochemical advantage: one of the conversion steps has already been completed. But this pattern cannot be extrapolated to any product and any skin.
The amount of retinoic acid formed depends not only on the starting molecule but also on penetration into the skin, enzyme activity, the base of the formula, and individual metabolism.
Retinal has clinical studies, including at concentrations of 0.05% and 0.1%. For example, in a small three-month study, both concentrations improved skin texture parameters. A reduction in the melanin index was noted only in the 0.1% group. At the same time, no convincing differences between the two concentrations were found for a number of other parameters.
Therefore, if your skin tolerates retinal well, using it in your routine is more logical. However, do not be too disappointed if you have sensitive skin—retinol will essentially provide a comparable effect.
Retinyl esters: additional helpers
This group includes:
- RETINYL PALMITATE: retinyl palmitate.
- RETINYL ACETATE: retinyl acetate.
- RETINYL PROPIONATE: retinyl propionate.
- RETINYL LINOLEATE: retinyl linoleate.
These substances are esters of retinol. To participate in the classic retinoid pathway, they first require hydrolysis, during which the ester group is removed and retinol is released. After that, the further chain of conversions begins.
Because of the additional steps, esters are often considered a gentler alternative to retinol. However, an important caveat should be made here: lower activity does not equal proven clinical gentleness, and good tolerability does not mean proven efficacy against wrinkles.
Different esters may differ in stability, release rate, and behavior within a formula. They cannot be regarded as one completely homogeneous group.
Retinyl palmitate is particularly illustrative. It is widely used in cosmetics and well known to manufacturers, but there is little clinical data allowing a confident assessment of its standalone efficacy against signs of photoaging. Systematic reviews note that the evidence for individual retinyl esters is significantly weaker than would be desirable for confident comparative recommendations.
Therefore, products with esters may be an option for those seeking a product with a retinoid ingredient, but expectations should be aligned with the available data. A pronounced effect against wrinkles cannot be guaranteed solely on the basis of RETINYL PALMITATE being present in the composition.
HPR: a promising representative of the retinoid class
INCI: HYDROXYPINACOLONE RETINOATE
HPR, or hydroxypinacolone retinoate, is often encountered under the marketing name Granactive Retinoid.
Unlike retinol and retinal, HPR is usually described as a compound capable of interacting with retinoic acid receptors (RAR) without undergoing the classic sequence of conversions. This is precisely what explains the interest in it as a potentially well-tolerated alternative to traditional retinoids.
Clinical data on HPR are still limited, but studies are gradually emerging.
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In a 2023 study involving 42 women, a serum with a combination of HPR and retinyl propionate improved wrinkle parameters, smoothness, and skin elasticity over eight weeks, identifying the combination of retinyl propionate and hydroxypinacolone retinoate as particularly successful. The formula was named Gravi-A.
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In a study published in 2025 in the Journal of Cosmetic Dermatology, a serum with 0.1% HPR and 9.5% peptides was compared with a single session of fractional CO₂ laser. The study involved 71 women: 42 used the serum twice daily for 16 weeks, and 29 underwent the laser procedure.
According to the results, the serum showed statistically more pronounced improvement in a number of parameters, including wrinkles, skin texture, hyperpigmentation, and signs of photoaging. For other parameters, the results were comparable to the laser.
These results are encouraging, but they are still insufficient for a confident comparison of HPR with retinol and retinal in terms of efficacy.
Prescription retinoids: a separate category
Tretinoin, adapalene, tazarotene, and trifarotene belong to the class of medicinal retinoids. Their status and availability depend on the country, but they should be evaluated primarily as medications for specific dermatological indications, not as yet another option for cosmetic skincare.
Tretinoin is all-trans retinoic acid. It does not need to undergo the conversion chain described above from retinol. It is for tretinoin that the most convincing clinical evidence base exists for correcting photoaging among topical retinoid medications.
Adapalene acts differently. It has an affinity for certain subtypes of retinoid receptors and is widely used for acne. Tazarotene is a retinoid specialized for the treatment of psoriasis. Trifarotene is the youngest of the four. It is a new-generation retinoid approved in the United States in 2019. It targets one specific skin receptor very precisely, which is why it works effectively while causing fewer side effects. It can be applied to large areas of skin, including the back and chest.
This distinction has practical significance. If the goal is to treat inflammatory acne, prescription retinoids may have a significantly more appropriate evidence base than a cosmetic serum with retinol. But the choice of medication, concentration, and regimen depends on the skin condition and must take into account the risk of irritation.
Bakuchiol: an alternative to retinoids
INCI: BAKUCHIOL
Bakuchiol is often advertised as a plant-based alternative to retinol. However, from a chemical and mechanistic standpoint, it is a different substance. It does not undergo the classic chain of conversion from retinol to retinoic acid and is not its direct equivalent in terms of mechanism of action.
Bakuchiol has antioxidant properties, as well as clinical data indicating potential benefits for certain signs of photoaging. But it does not follow from this that it fully replaces retinoids in terms of efficacy.
Although bakuchiol is recommended for pregnant and breastfeeding women seeking a safe alternative to vitamin A serums, there are insufficient studies on its non-toxicity. But there is also no data confirming toxicity.
In general, with normal use (a serum once a day before bed on the face), neither bakuchiol nor retinol, as a rule, has an effect on the fetus.
2. How retinoids work within the skin
The skin is not a passive surface through which an active ingredient simply passes to its destination. It is a living tissue with enzymes, transport proteins, and regulatory mechanisms. Part of the substance may remain in the surface layers, part will be metabolized, and part will not reach the biological target in a significant amount.
For retinol, retinal, and their esters, the classic pathway is as follows.
Step 1. Retinyl esters are converted to retinol.
Esterase enzymes carry out the hydrolysis of the ester bond. Before this step, the substance cannot simply proceed to the next stage of the classic pathway.
Step 2. Retinol is converted to retinal.
Oxidation occurs with the participation of alcohol dehydrogenase and retinol dehydrogenase enzymes. This process is regulated by the cell and is reversible under certain conditions. Therefore, not all retinal formed will necessarily continue along the chain.
Step 3. Retinal is converted to retinoic acid.
This is the key step of the classic pathway. It occurs with the participation of enzymes of the ALDH1A family, also called retinaldehyde dehydrogenases or RALDH. Unlike the previous step, this reaction is considered irreversible within this chain.
Step 4. Retinoic acid regulates cellular processes.
Retinoic acid can bind to proteins involved in its intracellular transport. It then interacts with nuclear RAR receptors, which function in complex with RXR.
This complex participates in the regulation of gene transcription, that is, it influences which proteins the cell will produce and in what quantity. This is precisely why the action of retinoids cannot be reduced solely to accelerated exfoliation of the skin surface.
It is a matter of broader influence on keratinocyte differentiation, epidermal structure, and dermal remodeling processes. Retinoids can support the synthesis of extracellular matrix components, including type I procollagen and fibrillin, as well as influence the activity of matrix metalloproteinases involved in the breakdown of its components.
These processes are related to visible skin changes: fine lines, uneven relief, certain manifestations of photoaging, and uneven pigmentation.
Here it is important not to overestimate the scale of the effect. A retinoid does not return the skin to its original state within a few weeks and does not eliminate all causes of wrinkle formation. The clinical result develops gradually, and its severity depends on the initial condition of the skin, duration of use, photoprotection, and the specific composition of the product.
3. Why a short conversion chain does not guarantee a better result
In the classic sequence, it is convenient to compare the number of required steps:
retinyl esters → retinol → retinal → retinoic acid.
The closer the starting molecule is to retinoic acid, the fewer chemical conversions it requires. But this is only one part of the explanation for efficacy.
Let us imagine two products: one contains retinol 0.5%, the other retinal 0.1%. One cannot simply compare the numbers or the number of steps and guarantee that one of them will necessarily produce a more pronounced result.
At least four factors influence the outcome.
First factor: penetration. The molecule must reach the right layers of the skin. This is influenced by its physicochemical properties and the base of the product.
Second factor: stability. The retinoid must remain in the formula during production, storage, and use. A substance sensitive to light and oxygen may gradually degrade, even if the initial concentration was correctly stated.
Third factor: metabolism. The amount of active metabolite depends on enzyme activity and the cellular environment. The same percentage does not guarantee the same amount of retinoic acid in the skin in different people.
Fourth factor: tolerability. If a product causes pronounced irritation and has to be constantly discontinued, the real result may be worse than that of a more moderate formula that the person uses regularly.
In studies on skin models, the penetration of various retinoids and the formation of their metabolites were measured. For example, in experiments with a three-dimensional skin model, retinol and retinal formed a more pronounced depot of the starting substance than retinyl palmitate. At the same time, the formation of retinoic acid from palmitate was not detected under the specific experimental conditions.
Such results help explain possible differences between compounds. But a laboratory model does not fully reproduce living human skin, and the results of a single experiment cannot be turned into a universal ranking of all cosmetic formulas.
Practical conclusion: biochemical proximity to retinoic acid is useful for understanding the mechanism of action, but by itself it is insufficient for predicting clinical efficacy.
4. What clinical studies show
The difference between a biochemical mechanism and a real result is especially visible when comparing studies.
In the laboratory, one can detect a change in the expression of a certain gene or an increase in the amount of an extracellular matrix component. In a clinical study, a different level of result is assessed: how much wrinkles, texture, pigmentation, hydration, or tolerability have changed in people.
Both types of data are needed. But they answer different questions.
Tretinoin: a strong clinical evidence base
Studies of tretinoin, including the classic work of Kligman and colleagues, played an important role in the development of topical therapy for photoaging. The use of tretinoin has been associated with improvement in a number of signs of UV-damaged skin, including fine lines, roughness, and pigmentation disorders.
At the same time, tretinoin has a characteristic drawback: irritation, dryness, peeling, and redness can limit regular use.
It is precisely this problem that largely explains the interest in cosmetic precursors of retinoic acid. Manufacturers strive to obtain the benefit while maintaining acceptable tolerability.
Retinol versus tretinoin: where the 1:10 ratio came from
In a 2015 study by Babcock and colleagues, several formulas with retinol and tretinoin were compared. The study included 65 participants who completed 12 weeks of observation. The comparison was conducted on half-faces.
The following concentration pairs were used: retinol 0.25% versus tretinoin 0.025%, retinol 0.5% versus tretinoin 0.05%, and retinol 1% versus tretinoin 0.1%.
In both groups, improvements in a number of photoaging parameters were observed. No statistically significant differences between the compared products were found for the main efficacy parameters.
At first glance, this confirms the popular rule according to which retinol is approximately ten times weaker than tretinoin. But there is a significant detail: the study evaluated specific formulas with controlled-release retinol. Its results cannot be automatically extrapolated to all products with retinol.
Therefore, the 1:10 ratio should not be perceived as a universal conversion coefficient. It is an observation from a specific study, not a formula allowing one to calculate the equivalent concentration of any product from the label.
Retinol 0.3% versus 1%: more is not always better
In a study published in the International Journal of Cosmetic Science in 2022, the effect of different retinol concentrations on skin structure parameters and tolerability was examined.
In the laboratory part of the study, skin samples obtained from five participants were evaluated. In a separate part, 218 people used products with retinol 0.3% or 1% according to a gradually increasing regimen for six weeks.
Both concentrations demonstrated an effect on certain markers of cell proliferation and dermal remodeling. At the same time, the product with retinol 0.3% was tolerated better than the formula with 1%.
This does not prove that 0.3% is always more effective than 1%. The study evaluated specific formulas, specific biological parameters, and a limited duration of use. However, it clearly shows why increasing the concentration is not necessarily justified.
If a lower concentration already provides the necessary effect, the additional irritation from a higher dose may not provide comparable practical benefit.
Retinal 0.05% versus 0.1%: results are not identical across all parameters
In a study by Kwon and colleagues, published in 2018, 40 women participated. They used creams with retinal 0.05% or 0.1% twice daily for three months.
In both groups, improvements in the overall assessment of photoaging and skin texture were noted. Transepidermal water loss, hydration, and the melanin index were also assessed.
A reduction in the melanin index was found in the 0.1% group, whereas for a number of other measured parameters there were no statistically convincing differences between the two concentrations.
This result is of interest for products targeting uneven skin tone. But it does not mean that 0.1% retinal is a proven universal solution for any pigmentation. The study evaluated a specific formula and a limited group of participants, and pigmentation itself can have different causes.
Retinal in multilamellar vesicles: the importance of the formula
In another study, retinal in a multilamellar vesicle system was compared with retinol at similar concentrations. The study involved 23 people, and observation continued for eight weeks.
The authors evaluated several photoaging parameters and found improvements with the use of the studied products. For some parameters, the formulas with retinal demonstrated more pronounced changes.
There is an important caveat here: the study compared not only the molecules but also their delivery methods. If one substance is in a special release system and the other in a conventional base, the final result cannot be explained solely by the chemical nature of the retinoid.
Therefore, such studies are especially interesting from the standpoint of formula development, but they do not provide grounds for asserting that retinal in any cosmetic product is superior to retinol.
HPR in combination with retinyl propionate
In a 2023 study by Wang and colleagues, a combination of HPR and retinyl propionate was examined. The clinical part included 42 participants and continued for eight weeks.
The authors reported improvements in certain parameters of wrinkles, smoothness, and skin elasticity. Transepidermal water loss and laboratory markers related to retinoid metabolism were also assessed.
But here it is fundamentally important that a combined formula was studied. One cannot automatically attribute the entire result exclusively to HPR, determine the contribution of each component, or draw a conclusion about the superiority of HPR over retinol.
The small number of participants and the short observation period also limit the strength of the conclusions. For a confident comparison, additional high-quality studies are needed, including direct comparisons of individual substances in comparable formulas.
What can ultimately be considered proven
Studies provide grounds for considering that topical retinoids are capable of improving certain signs of photoaging. However, the volume and quality of evidence differ substantially for different compounds.
The most convincing clinical evidence base exists for tretinoin as a medicinal product. Among cosmetic retinoids, retinol is widely studied, and retinal has promising clinical data. For individual retinyl esters and HPR, there is noticeably less evidence, especially when it comes to their standalone efficacy at a specific concentration.
Consequently, comparing ingredients solely by published improvement percentages is incorrect. Results depend on the composition, study methodology, number of participants, duration of observation, and the selected endpoints.
5. Which retinoid to choose for a specific task
The choice depends not only on the desired effect but also on the condition of the skin barrier, previous experience with active ingredients, and readiness to follow a regular regimen.
If you are starting to use retinoids
For a start, it is more reasonable to choose a product with a low concentration of retinol, for example 0.1–0.3%, or a formula with a small amount of retinal, if it is suitable in terms of the stated concentration and tolerability.
One usually starts with two evenings per week, gradually increasing the frequency if tolerability is good.
There is no need to specifically strive for peeling. The absence of irritation does not mean that the product is not working. If the skin remains calm, this rather allows the product to be used regularly, which is important for obtaining a result.
With pronounced sensitivity, active dermatitis, or a damaged barrier, the introduction of a retinoid is better postponed until the skin has recovered.
If the main goal is fine lines and signs of photoaging
For cosmetic skincare, retinol or retinal in a formula with a clear concentration and good stabilization can be considered.
Retinol 0.3% may be a reasonable starting point for a person who is already familiar with active ingredients and tolerates them well. Retinal 0.05–0.1% also belongs to the options with clinical data on improving texture and certain signs of photoaging.
But there is no universally best option. For a long-term result, it is more important to find a product that can be used regularly without persistent irritation than to periodically use an excessively active formula.
If pigmentation and uneven tone are a concern
Retinoids can help with certain pigmentation disorders, but the result depends on the cause of the skin color change.
For example, post-inflammatory hyperpigmentation after inflammation and injuries, melasma, and pigmentation due to chronic ultraviolet exposure are not the same condition. One product does not have to work equally effectively in all these cases.
For retinal 0.1%, there is a small clinical study in which an improvement in the melanin index was found. This is an interesting result, but not proof of universal action against any pigmentation.
Daily photoprotection is mandatory as part of skincare. Ultraviolet radiation can maintain pigmentation and intensify photoaging, so a retinoid alone does not replace full protection from the sun.
If comedones and visible pores are a concern
Retinoids can improve the condition of skin prone to comedones, as well as visual texture. But it is important to distinguish between pore blockage and their anatomical size.
If the problem lies predominantly in closed or open comedones, the treatment regimen may differ from skincare aimed at wrinkles and photoaging. For pronounced acne, cosmetic retinol should not be considered a full replacement for medical treatment.
Adapalene, tretinoin, and other medicinal retinoids are used for certain forms of acne. The choice depends on the severity of the disease, tolerability, and other components of treatment.
If retinol irritates the skin
First, it is worth determining whether the problem is truly related to the retinoid itself or to a combination of several active ingredients, frequency of application, cleansing, and the condition of the barrier.
Sometimes it is enough to reduce the frequency of use, switch to a lower concentration, or temporarily restore the barrier.
HPR and retinyl esters can be considered as alternatives.
6. How to read the label and evaluate the formula
Knowledge of INCI helps identify the retinoid, but to evaluate a product, several additional details need to be taken into account.
Look not only at the name but also at the concentration
If a manufacturer claims 1% retinoid complex, attention should be paid to the wording: it refers specifically to a complex, not to the pure active substance. Such a complex may include several components, each in its own concentration.
Therefore, it is more reliable to look for data on the content of each ingredient separately, since only in this way can the real concentration of the active substance in the formula be assessed.
Do not try to calculate the percentage solely from the ingredient’s position in the INCI list
There is a popular piece of advice to look for the retinoid closer to the beginning or the end of the list. But here everything depends on labeling rules and the concentration of the ingredient.
In many labeling systems, substances present in small amounts may be listed in arbitrary order after ingredients with a concentration above a certain threshold. For example, in the United States, ingredients with a concentration of no more than 1% may be listed not in descending order of concentration.
Therefore, the position of RETINOL or RETINAL in the list does not allow a reliable determination of the exact percentage. This requires information from the manufacturer.
Take packaging and stabilization into account
Retinol and retinal are sensitive to light, oxygen, and storage conditions. An opaque tube or high-quality airless packaging can reduce exposure to air and light, but by itself does not guarantee the stability of the product.
The entire formula matters: the stabilizers used, the production technology, the compatibility of components, and the results of stability testing.
The presence of tocopherol or BHT in the composition is not independent proof that the retinoid is fully protected from degradation.
Unlike some acids, for retinoids there is no single universal pH value by which the quality of a formula can be assessed. Here, the combination of characteristics of the finished product is more important.
Take legislative requirements into account
The norms depend on the country and the specific substance.
For example, in the European Union, Regulation (EU) 2024/996 establishes restrictions specifically and exclusively for retinol, retinyl acetate, and retinyl palmitate: up to 0.05% calculated as retinol equivalent for body lotions and up to 0.3% for other cosmetic products covered by the regulation. For certain products, mandatory warning labeling about vitamin A content is also provided.
These restrictions apply specifically to the listed substances and EU rules. They cannot be automatically extrapolated to all retinoids, all countries, and any products labeled Retinoid Complex.
7. How to introduce a retinoid without pronounced irritation
The correct application regimen is no less important than the choice of molecule.
Start with a low frequency. For the first two weeks, the product can be used twice a week. If the skin tolerates it well, the frequency is increased gradually. Switching to daily use is not obligatory if a less frequent regimen is already well tolerated and corresponds to the product instructions.
Apply to dry skin. This is especially useful for people prone to irritation. Moist skin can alter the penetration pattern of certain ingredients.
Use a small amount. For most products intended for the entire face, a small pea-sized portion is a guideline, unless the manufacturer’s instructions provide otherwise.
Do not forget about moisturizing. A cream after the retinoid or the use of a moisturizing product before it can help reduce discomfort. The specific regimen should be chosen taking tolerability into account.
Do not add several irritating actives at once. At the initial stage, it is reasonable not to use a retinoid and high-concentration AHA/BHA peels on the same evening. This does not mean that combinations are always prohibited, but the simultaneous introduction of several active ingredients makes it difficult to understand the cause of possible irritation.
Use photoprotection. In the morning, apply a broad-spectrum sunscreen suitable for daily use. This is especially important when dealing with pigmentation and signs of photoaging.
In the first weeks, moderate dryness or slight peeling may occur. However, pronounced redness, persistent burning, cracks, swelling, and soreness should not be considered an obligatory part of adaptation. With such symptoms, the frequency should be reduced or use discontinued until the skin recovers.
A retinoid does not have to cause irritation in order to have an effect. A sustainable regimen that the skin tolerates is usually more beneficial than constantly alternating between intensive use and forced breaks.
8. Pregnancy and breastfeeding
Retinoids require separate discussion during pregnancy and breastfeeding.
During pregnancy, topical retinoids are recommended to be avoided as a precautionary measure. Systemic retinoids can cause severe fetal developmental disorders. When applied topically, absorption is usually significantly lower, but due to the potential risk and limited data, cosmetic and medicinal topical retinoids are not recommended for use during pregnancy.
When planning a pregnancy, the question of discontinuing a specific medication should be discussed with a doctor in advance, especially if it is a medicinal product.
During breastfeeding, the data differ from the situation with pregnancy. For example, the LactMed database indicates that topical tretinoin is poorly absorbed through the skin and, when applied topically, is considered a medication with low risk for the child, although direct studies of its use during lactation are insufficient.
At the same time, tretinoin must not be applied to the nipples and areolae, and the child’s skin must not come into contact with treated areas. For cosmetic retinoids, direct data are also scarce, so the individual choice of product is best coordinated with a doctor.
Thus, the statement that absolutely all retinoids without exception are contraindicated during breastfeeding would be overly categorical. But automatically considering any cosmetic product safe simply because it is applied to the skin is also wrong.
9. Frequently asked questions
Retinol or retinal: which is stronger?
Retinal is one step closer to retinoic acid in the classic conversion chain. This is an important biochemical difference, but it does not guarantee the superiority of any product with retinal over any product with retinol.
For comparison, concentration, formula stability, delivery system, and specific clinical data need to be taken into account.
Is HPR stronger than retinol?
To date, there is insufficient quality comparative data to state this confidently. HPR is interesting for its claimed mechanism of interaction with receptors and preliminary clinical results, but the evidence base is still smaller than that of retinol and medicinal retinoids.
Moreover, studies of combined formulas with HPR do not allow the effect of a single ingredient to be isolated.
Is retinyl palmitate useless?
No. It is not automatically a useless ingredient. However, the standalone efficacy of retinyl palmitate against wrinkles and other signs of photoaging has not been studied well enough to recommend it as an equivalent replacement for retinol or tretinoin.
If a product contains retinyl palmitate, it is worth evaluating the entire formula and the actual data on its efficacy, not just the name of the ingredient.
When can results be expected?
Results depend on the task and the formula. The first changes in texture may become noticeable after a few weeks, but it is more reasonable to evaluate the effect against wrinkles and signs of photoaging after several months of regular use.
Timeframes of 4–8 weeks for early changes and 12–24 weeks for assessing longer-term results can be used as guidelines, but not as a guarantee for every person.
Does bakuchiol replace a retinoid?
It can be an alternative ingredient in skincare, but it is not a chemical or mechanistic equivalent of retinoids. Data on certain beneficial effects exist, but direct comparison of efficacy is limited.
Is a retinoid with a higher concentration better?
No. Increasing the concentration may increase the risk of irritation, but will not necessarily produce a proportional increase in effect. For a practical result, formula stability, regularity of use, and tolerability are important.
Conclusion
Retinoids share a connection to vitamin A, but the differences between them are fundamental. Retinol and retinal undergo the classic stages of conversion to retinoic acid, retinyl esters require additional conversions, and HPR is considered a separate option with a limited evidence base. Tretinoin and other medicinal retinoids have their own indications and should not be evaluated solely by the rules of cosmetic skincare.
When choosing a product, one should take into account not only the INCI and the percentage but also the evidence of efficacy, the characteristics of the formula, tolerability, and the purpose of use. The biochemical mechanism explains why substances may differ, while clinical studies show what changes were actually observed in people.
It is the combination of these two levels of information that allows retinoids to be chosen in an informed manner, without inflated expectations from loud marketing claims.
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