Retinoids remain the most extensively studied and clinically validated topical ingredient in skin science. Over the past four decades, the scientific literature has consistently demonstrated their ability to influence cellular behaviour, collagen production and epidermal renewal in measurable ways.
Yet despite this depth of evidence, retinoids are often misunderstood. Questions around potency, irritation, purging, percentage strength and long-term structural impact continue to circulate.
I want to step beyond usage tips and explore what retinoids are actually doing at a biological level. Understanding the mechanism allows you to use them with greater confidence, greater precision and realistic expectations.
In this article:
- The Science Behind Retinoids
- Understanding Strength and Conversion
- Adjustment, Purging and Tolerance
- Retinoids for Skin Conditions
- How to Use Retinoids Safely and Effectively
- Building a Retinoid Routine
- Results, Skin Change and A Low and Slow Approach
What is a retinoid and how does It work?
A retinoid is any topical compound derived from vitamin A that influences cellular behaviour within the skin. What makes retinoids unique is not simply that they increase cell turnover, but how they do it.
Retinoids bind to retinoic acid receptors (RARs) within skin cells. Once bound, they regulate gene expression. This signalling cascade influences how keratinocytes – the primary cells of the epidermis – proliferate, differentiate and shed, and how fibroblasts synthesise collagen and elastin, the structural proteins that give skin its firmness and elasticity.
At the surface, retinoids accelerate the shedding of damaged corneocytes in the outermost layer of the skin – the stratum corneum. Beneath the surface, they stimulate the generation of new, healthier cells and reinforce dermal structure.
I often describe this as a dual mechanism. Exfoliation from above. Regeneration from below.
With consistent use, retinoids are associated with measurable biological changes including increased epidermal thickness, improved barrier function and reduced collagen degradation. These structural responses underpin the visible improvements we observe in skin texture, tone and resilience.
In clinical practice, the form of retinoid chosen can significantly influence how well your skin tolerates it and the results you can expect. To understand how potency and performance differ, it's helpful to look at the three most commonly used topical retinoids: retinol, retinal and tretinoin.
What's the difference between retinol, retinal and tretinoin?
Retinol, retinaldehyde and tretinoin are all forms of vitamin A, but they differ in how directly they act within the skin.
For any retinoid to work, it must ultimately convert to retinoic acid. That is the active form the skin can actually use.
Retinol requires two conversion steps inside the skin. It first converts to retinaldehyde, and then to retinoic acid. Because of this, retinol tends to work more gradually and is generally well tolerated. It is also widely available without prescription in cosmetic formulations under 1% w/w, although quality and stability can vary between brands.
Retinaldehyde, often shortened to retinal, requires only one conversion step before becoming retinoic acid. That means it can work more efficiently than retinol at lower concentrations. It also demonstrates antibacterial activity, which can provide additional benefit in acne-prone skin without the same level of irritation often associated with stronger prescription retinoids.
Tretinoin is retinoic acid itself. It does not need to convert and acts directly on skin cells. It is available by prescription and has the strongest evidence base for photoageing and acne. However, because it works immediately at full strength, it also carries a higher likelihood of irritation, dryness and peeling, especially during the early stages of use.
In simple terms, the fewer conversion steps required, the stronger and faster the effect. But greater strength also increases the potential for sensitivity. Choosing the right retinoid is not just about potency. It is about matching the ingredient to your skin’s tolerance and long-term goals.
What is retinoid purging and is it normal?
An initial adjustment phase is common when introducing a topical retinoid to your skin.
For some people, this presents as an increase in breakouts. For others, it appears as dryness, flaking, tightness or redness. These changes can feel alarming, particularly if you are new to vitamin A.
Purging specifically refers to the accelerated surfacing of pre-existing microcomedones. As cell turnover increases, congestion that was already forming beneath the surface is brought forward more quickly. In practice, this can look like small breakouts appearing in areas where you typically experience congestion. Once released, these blemishes tend to resolve more quickly than usual rather than remaining trapped beneath the surface.
This process typically begins within the first one to two weeks and settles within four to eight weeks as the skin adapts.
However, not all irritation is purging.
A true adverse reaction is more likely to present as widespread inflammation, persistent redness, stinging or rash, particularly in areas where you would not normally experience breakouts.
The key distinction is pattern and duration. Purging follows your usual breakout areas and improves with continued, appropriate use. A reaction worsens or spreads.
If symptoms are severe or persistent, pause use temporarily and follow professional advice before continuing.
Most importantly, understand that adaptation is part of the biological response. Retinoids alter cellular signalling. This is not about stopping altogether but allowing your skin time to recalibrate before reintroducing them gradually.
Do retinoids thin the skin?
No. This is one of the most persistent myths surrounding vitamin A.
Retinoids do not thin the skin. In fact, with consistent use, they increase epidermal thickness by stimulating cell proliferation in the basal layer.
The confusion arises during the initial adjustment phase. As retinoids accelerate cell turnover, the outermost layer of dead cells – the stratum corneum – sheds more rapidly. During this period, the skin can feel thinner, drier or more sensitive.
However, this surface shedding is temporary and does not reflect thinning of the living layers beneath.
Over time, these living layers – of the epidermis and the underlying dermis – become thicker and more structurally robust. This structural reinforcement is one of the key mechanisms behind the efficacy of retinoids for anti-ageing.
Understanding this distinction is critical. Increased surface renewal does not mean structural thinning. It reflects biological activity and the normalisation of skin function.
What does a retinoid do for ageing skin?
Retinoids are the most evidence-based topical ingredient for reducing visible signs of skin ageing. Their strength lies in their ability to influence both the surface of the skin and the deeper dermal structures.
At a cellular level, retinoids stimulate fibroblast activity to increase collagen and elastin synthesis. These structural proteins are responsible for skin firmness, elasticity and resilience. By supporting their production and reducing collagen degradation, retinoids help reinforce the underlying framework of the skin.
At the same time, accelerated cell turnover helps fade hyperpigmentation, smooth uneven texture and restore skin luminosity. As older, damaged cells are shed more efficiently, the surface appears smoother and more even.
Peer-reviewed research spanning over 40 years confirms that consistent retinoid use leads to measurable improvements in epidermal thickness, dermal collagen density and overall skin architecture. These changes are progressive rather than immediate.
Most people notice improvements in texture within 8 to 12 weeks. More visible changes in firmness and line depth typically develop over 6 to 12 months of consistent use.
Retinoids are not a quick fix. Their benefits build gradually and compound over time.
Can retinoids help with acne and breakouts?
Yes. Retinoids work through multiple pathways and play a central role in managing acne-prone skin.
One of the primary drivers of acne is abnormal shedding of cells within the follicular lining. When dead cells and sebum accumulate, pores become clogged, forming comedones (blackheads and whiteheads). Retinoids normalise this shedding process, helping to prevent the build-up that leads to congestion in the first place.
They also reduce skin inflammation, which is a key driver of acne lesions. Some forms, particularly retinaldehyde, have demonstrated direct antibacterial activity, adding another layer of benefit in acne-prone skin.
Retinoids are effective across the acne spectrum, from mild comedonal acne to more persistent inflammatory breakouts. Because they address both active congestion and the underlying process that leads to clogged pores, they are one of the few topical ingredients that can support clearer skin while also improving the appearance of post-inflammatory marks over time.
On Retinoid Purging
As outlined earlier, purging can occur during the initial weeks of use as pre-existing microcomedones surface more rapidly.
In acne-prone skin, this phase may feel more pronounced, but it remains temporary. Purging typically begins within the first one to two weeks and settles within four to eight weeks as the skin adapts.
If breakouts occur in areas where you would not normally experience congestion, or are accompanied by persistent irritation or rash, this may indicate a reaction rather than purging and professional guidance should be sought before continuing use.
Can retinoids help with hyperpigmentation?
Yes. Retinoids play an important role in improving hyperpigmentation and uneven skin tone.
They do this through several mechanisms. First, by accelerating epidermal turnover, retinoids promote the more efficient shedding of pigment-laden keratinocytes. As these cells are replaced, overall tone can appear clearer and more even.
Melanin production begins inside pigment-producing cells called melanocytes. Within these cells, an enzyme called tyrosinase initiates the biochemical pathway that forms pigment.
Retinoids influence melanocyte behaviour indirectly by regulating cellular signalling within the epidermis. While they are not direct pigment inhibitors in the way that some tyrosinase-targeting ingredients are, they help normalise melanin distribution and improve the dispersion of excess pigment within the skin.
In cases of post-inflammatory hyperpigmentation, retinoids are particularly useful because they address both the underlying inflammatory cascade and the retention of pigment within the epidermis.
As with all retinoid benefits, improvement is progressive. Consistent use over several months is typically required to see meaningful changes in tone uniformity.
How do I start using a retinoid without irritating my skin?
Introducing a retinoid successfully is not about starting at the highest strength. It is about building tolerance intentionally.
I recommend a "low and slow" approach.
Begin with a lower-strength formulation that is appropriate for your skin type and previous retinoid experience. Apply it two to three nights per week for the first two to four weeks. This allows the skin time to adapt to increased cellular turnover.
Use a pea-sized amount on clean, dry skin. Applying retinoids to damp skin can increase penetration and, in turn, irritation.
If needed, you can buffer the retinoid by applying a hydrating serum or moisturiser beforehand. This does not prevent the retinoid from working. It simply moderates the rate at which it penetrates during the early stages of use.
During the early stages, avoid layering strong resurfacing ingredients such as glycolic acid, lactic acid or salicylic acid in the same routine. Allow your skin to adjust to the retinoid first before introducing additional actives.
Over time, frequency can be increased gradually, typically over six to eight weeks, until nightly use is achieved if tolerated.
During the adjustment phase, mild dryness, light flaking and transient redness are common. These are signs that cell turnover is increasing. They should reduce as the skin acclimatises.
Barrier-supportive ingredients such as niacinamide, ceramides and hyaluronic acid can be used alongside a retinoid to maintain comfort and resilience.
I always advise treating the retinoid as the anchor active in your routine – the ingredient everything else is built around. Let it do the heavy lifting and build the rest of your skincare around it thoughtfully to avoid layering multiple exfoliating ingredients at once, which can lead to irritation or a reaction.
Should I use retinoids in the morning or at night?
Retinoids should be applied at night.
Retinol and retinaldehyde are photolabile, meaning they degrade and lose efficacy when exposed to ultraviolet light. Daytime application reduces their stability and effectiveness.
Night-time use also aligns with the skin’s natural circadian repair cycle, when cell turnover and regeneration are most active.
Daily broad-spectrum SPF 50 is non-negotiable when using any retinoid. Increased cell turnover temporarily reduces the thickness of the stratum corneum, which can increase photosensitivity. This heightened sensitivity persists even on days when the retinoid is not applied.
Can I use retinoids with Vitamin C, AHAs or Niacinamide?
Retinoids can be combined with other active ingredients, but they need to be introduced thoughtfully.
Niacinamide is an excellent pairing. It strengthens the skin barrier, reduces inflammation and helps mitigate retinoid-related irritation. It can be used in the same routine.
Vitamin C (L-ascorbic acid) is best used in the morning, with retinoids reserved for the evening. This separation maximises the antioxidant and photoprotective benefits of vitamin C during the day and allows the retinoid to work alongside the skin’s circadian repair cycle at night.
AHAs and BHAs, such as lactic acid, glycolic acid and salicylic acid, require more caution when used alongside a retinoid. As these acids are exfoliating, layering them in the same routine as a retinoid can compromise barrier integrity.
For established retinoid users with resilient skin, alternating nights may be appropriate. For most people, I prioritise the retinoid as the anchor active – the ingredient the routine is built around – and introduce additional acids only once full tolerance is established.
The general principle is to avoid stacking multiple exfoliants simultaneously. Build complementary ingredients around the retinoid rather than competing with it.
Can I Use Retinoids on the Eye Area and Neck?
Yes, with appropriate formulation and care.
The skin around the eyes, as well as the neck and décolletage, is thinner and often more reactive than the rest of the face. This makes these areas more susceptible to irritation if a retinoid is introduced too quickly or at too high a concentration.
When extending retinoid use beyond the face, I recommend starting with a lower concentration or a formulation specifically designed for delicate areas. Apply sparingly and avoid the immediate lash line and eyelids.
For the neck and chest, introduce the retinoid gradually – beginning one to two nights per week and increasing frequency as tolerated. These areas are highly prone to photodamage and collagen loss, making them excellent candidates for retinoid support, but they require a more measured approach.
As with facial application, monitor the skin’s response and prioritise barrier support if signs of irritation occur. Precision and patience are more important than strength.
Who should not use retinoids?
Retinoids are contraindicated during pregnancy and breastfeeding.
Oral retinoids, such as isotretinoin, are known teratogens, substances that can cause birth defects. While systemic absorption from topical retinoids is minimal, dermatological and obstetric authorities advise avoiding all retinoid use during pregnancy and breastfeeding as a precautionary measure.
Retinoids may also not be suitable for individuals with:
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Active eczema or dermatitis.
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A significantly compromised skin barrier.
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Rosacea or highly reactive skin, without professional supervision.
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Recent ablative procedures, such as laser resurfacing, deep chemical peels or microneedling, where a recovery period is required before reintroduction.
If you are unsure whether a retinoid is appropriate for your skin, seek guidance from your prescribing clinician or dermal therapist for personalised advice.
How long does it take to see results from a retinoid?
Retinoid results follow a progressive timeline. They are cumulative, not immediate.
In the first two to four weeks, the skin may feel smoother to the touch as surface cell turnover increases. Some dryness, flaking or mild purging may occur during this early adjustment phase.
Between six and twelve weeks, more visible improvements in texture and tone typically become apparent. Skin often appears more even, and superficial fine lines may look softer as renewal processes continue. Post-inflammatory marks may also begin to fade.
By three to six months, changes in firmness and pore refinement become more noticeable. Collagen signalling and structural reinforcement are ongoing during this period.
At six to twelve months and beyond, benefits compound. Long-term retinoid users demonstrate measurable increases in skin density and epidermal thickness. These changes reflect structural adaptation rather than temporary surface improvement.
Consistency is the critical ingredient. A lower-strength retinoid used consistently will outperform a higher-strength product used sporadically. Retinoid benefits are cumulative and compound over time.
What percentage of retinoid should I use?
The ideal retinoid concentration depends on three factors: the type of retinoid, your skin’s tolerance history and your treatment goals.
Different forms of vitamin A are not directly comparable by percentage alone. Their biological activity depends on how many conversion steps are required before becoming retinoic acid.
Retinol
If you're just starting, begin between 0.01% and 0.3%, gradually building to 0.5% or 1.0% over time. Encapsulated or time-release formulations may improve tolerability, allowing for higher concentrations with reduced irritation.
Retinaldehyde (Retinal)
Retinal is more potent per unit because it requires only one conversion step. Effective concentrations typically range from 0.01% to 0.1%. A retinal at 0.05% can deliver comparable biological activity to a retinol at a significantly higher percentage.
Tretinoin (Prescription Retinoic Acid)
Tretinoin is typically prescribed between 0.025% and 0.1%, with the starting concentration determined by a clinician based on skin type and treatment goals.
It is important to understand that a higher percentage does not automatically mean better results. How well your skin builds tolerance, the consistency of use and the formulation quality are equally significant.
There is currently no regulatory requirement for brands to disclose retinoid percentage on cosmetic product labels. Look for brands that voluntarily declare clinically validated active concentrations. It is a marker of formulation transparency and evidence-based practice.
A low and slow approach
Retinoids remain one of the most transformative ingredients in skincare – not because they act quickly, but because they work at a cellular level.
Over my many years in the industry, and now as Brand Director of Aesthetics Rx® I have seen that the clients who achieve the best outcomes are not those chasing strength but are those who understand the biology and commit to consistency.
When introduced thoughtfully and used regularly, retinoids support long-term structural resilience, improved texture and greater clarity over time.
For me, vitamin A is not about speed. It is about precision.
Patience and consistency are what ultimately determine success.
Nicola Kropach, Brand Director