TL;DR
“Retinoid” is an umbrella term for a family of natural and synthetic compounds related to vitamin A. Retinyl esters, retinol and retinal are converted within the skin towards retinoic acid, while tretinoin is retinoic acid and can act without that conversion step.
Retinoids have one of the strongest evidence bases in skincare for improving fine lines, texture, photoageing and some forms of uneven pigmentation. The strongest option is not automatically the best one for you. Retinol and retinal are both good non-prescription options. I often favour retinal because it can offer a little more treatment activity with a broadly similar side-effect profile, and the range of available concentrations gives us room to adjust gradually rather than moving straight to prescription tretinoin.
The retinoid ladder in 30 seconds
The classic ladder describes the number of conversion steps between an ingredient and retinoic acid, the form that interacts with retinoid receptors in the skin:
Retinyl esters → retinol → retinaldehyde (retinal) → retinoic acid (tretinoin)
Retinyl esters need three conversion steps. Retinol needs two. Retinal needs one. Tretinoin needs none.
This helps explain the chemistry, but it is not a league table of finished products. A well-formulated retinol may be more useful than a poorly formulated retinal, and a lower-strength product used consistently may achieve more than a stronger one that repeatedly causes irritation. You cannot compare percentages directly across different molecules.
What do retinoids do?
Retinoids influence how skin cells grow, mature and communicate. Their effect is broader than simply “speeding up cell turnover”, and they are not conventional exfoliating acids.
The strongest evidence belongs to tretinoin. Controlled human studies have shown improvements in fine wrinkling, roughness and other features of photoaged skin [1]. Biopsy studies have also demonstrated changes consistent with increased type I collagen formation in photodamaged skin [2].
Retinoids can improve some forms of uneven pigmentation by affecting epidermal cell behaviour and the way pigment is distributed and removed through the skin. Tretinoin has improved hyperpigmented lesions associated with photoageing in controlled trials [3]. This does not make a retinoid a treatment for every dark mark. Melasma, post-inflammatory pigmentation, freckles and a changing pigmented lesion need different assessment and treatment.
Prescription retinoids are also established acne treatments because they help normalise follicular keratinisation and reduce comedone formation. Cosmetic retinol and retinal may suit some blemish-prone routines, but they are not interchangeable with prescribed acne treatment.
Results develop gradually. Texture may change before established pigmentation or fine lines, while collagen-related improvement is measured over months rather than days.
Stronger is not automatically better
In a 48-week controlled study, 0.025% and 0.1% tretinoin produced similar clinical and histological improvements in photoageing, while the higher concentration caused significantly more irritation [4].
That does not mean strength never matters. It means the highest concentration is not automatically the most effective choice in real life. If a product leaves you repeatedly inflamed, peeling or taking long breaks, a lower-strength option used steadily may achieve more.
How do the main retinoids differ?
Retinyl esters
Retinyl palmitate, retinyl propionate and retinyl acetate sit furthest from retinoic acid on the classic ladder. They are often used in gentler formulations and may suit a very cautious introduction to vitamin A. The trade-off is that the direct clinical evidence for visible change is less substantial than it is for retinol, retinal or tretinoin.
Retinol
Retinol is two conversion steps from retinoic acid. It has credible human evidence: controlled studies have reported improvements in fine wrinkling and changes in procollagen-related markers [5].
Retinol is highly formulation-dependent. It is sensitive to light and oxygen, so stabilisation, packaging and the vehicle affect how much useful ingredient remains by the time you apply it. A higher percentage does not automatically mean a better product.
Retinal
Retinaldehyde, usually shortened to retinal, is one conversion step from retinoic acid. Retinol and retinal are both reasonable non-prescription starting points. I often favour retinal for fine lines, texture or uneven tone because it can offer a little more treatment activity while retaining a broadly similar tolerability profile.
It offers a practical middle ground. It is closer to retinoic acid than retinol, but your skin still controls the final conversion. In a randomised study, 0.05% and 0.1% retinaldehyde creams improved skin texture and hydration after three months; the 0.1% formulation also improved the measured melanin index [6].
Retinal is not automatically mild or universally better than retinol. The formulation and starting strength still matter, and you should address an unsettled skin barrier before introducing any retinoid.
Tretinoin
Tretinoin is retinoic acid, so it does not need to be converted before acting in the skin. It has the deepest evidence base for photoageing, but its direct activity also brings a greater risk of redness, dryness, tightness and peeling.
Tretinoin may be appropriate when prescription treatment is suitable after individual assessment. It should be selected and reviewed as a medicine, rather than treated as the inevitable final rung of every cosmetic routine.
An option from the edit
A retinal with a graded step-up system
Doctor-selected • Treat
Medik8 Crystal Retinal
- Why I chose it
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I chose Medik8 Crystal Retinal because the graded strengths make it easier to begin at an appropriate level and progress only when your skin is ready.
- Best for
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You want a non-prescription retinal product with a graded step-up system.
- Usual place
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Use it in the evening after cleansing and before moisturiser.
- How to introduce it
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Start with a suitable lower strength on two evenings each week, then increase the frequency only when your skin is tolerating the current schedule. Moving to the next strength is optional.
- Another option may be better if
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Choose another route if your skin is actively irritated, you already use a prescribed retinoid, you are pregnant, planning pregnancy or breastfeeding, or you would prefer a gentler starting point. During pregnancy or breastfeeding, I would usually consider Medik8 Liquid Peptides Advanced MP as a retinoid-free evening alternative.
Where do AlphaRet and other retinoids fit?
Not every retinoid belongs neatly on the classic ladder. Adapalene and tazarotene, for example, are synthetic prescription retinoids with their own receptor activity and clinical uses.
AlphaRet is SkinBetter Science’s proprietary retinoid technology, combining a retinoid component with lactic acid in one molecule. A small 12-week split-face study found that the tested AlphaRet Overnight Cream formulation improved several visible measures of photodamage and caused less irritation than the comparison retinol and tretinoin products [7].
This is promising product-specific evidence, but it is much smaller than the accumulated evidence for tretinoin. The findings apply to the tested formulation rather than to every product with a newer or proprietary retinoid name.
An option from the edit
A proprietary retinoid formulation outside the classic ladder
Doctor-selected • Treat
SkinBetter Science AlphaRet Overnight Cream
- Why I chose it
-
I chose SkinBetter Science AlphaRet Overnight Cream as an example of why some retinoids need to be judged as complete formulations rather than placed on a simple conversion ladder.
- Best for
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You want a consultation-guided evening treatment combining retinoid and exfoliating activity.
- Usual place
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Use it after cleansing and before moisturiser if needed.
- How to introduce it
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Follow the introduction schedule agreed through The Curatory. Don’t add another retinoid or a separate exfoliating acid at the same time.
- Another option may be better if
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A simpler retinal product may be more appropriate if you want one main active, need a cautious starting point or are prone to irritation.
Which retinoid should you choose?
Choose according to your goals, previous experience and tolerance rather than selecting the strongest name or highest percentage.
Retinyl esters may suit you if you want the most cautious starting point and accept a less direct evidence base.
Retinol may suit you if you want a familiar, evidence-supported cosmetic retinoid in a well-stabilised formulation.
Retinal may suit you if you want a non-prescription middle ground with a more direct conversion pathway and the option to step up gradually.
Tretinoin may suit you if prescription treatment is appropriate after individual assessment and you understand the greater irritation potential.
AlphaRet or another proprietary formulation may suit you when the complete formula addresses a specific need and there is relevant evidence for that exact product.
Retinol and retinal are both good choices for a non-prescription routine. I usually lean towards retinal because it can do a little more with a similar side-effect profile, while the available concentrations give us room to adjust. That is a practical clinical preference rather than a rule for every skin type.
How to introduce a retinoid
Use a small amount in the evening on clean, dry skin. For many people, two non-consecutive evenings each week is a reasonable starting point. You can apply moisturiser before the retinoid, afterwards or both if this improves tolerability.
At first, avoid another retinoid or a strong exfoliating acid on the same evening. Keep the rest of the routine predictable and use broad-spectrum sunscreen every morning.
If your skin remains settled, you can gradually increase to three evenings each week and then, only if useful, alternate evenings. Nightly use and higher strengths are optional. There is no prize for completing the ladder.