Retinal vs retinol: why it’s stronger and how to use it
What retinal is and how it differs from retinol
Retinal (retinaldehyde) is a vitamin A derivative used in skincare that sits one step away from active retinoic acid in the metabolic pathway. It is a more advanced metabolite than retinol in the transformation cascade towards retinoic acid. It needs only one enzymatic conversion to become active; retinol needs two. That translates directly into speed and intensity of results on the skin.
In products like Medik8 Crystal Retinal, the retinaldehyde is stabilised to maintain its bioactivity and prevent premature oxidation. An oxidised retinal molecule before it penetrates the skin is essentially useless: that stabilisation is what separates a serum that delivers results from one that does very little.
- Retinal is a vitamin A derivative that requires a single enzymatic step to convert into active retinoic acid in the skin.
- Retinol needs two metabolic conversions to reach retinoic acid, so it usually acts more slowly than retinal.
- Stabilised retinal formulations reduce oxidation, helping maintain potency until the ingredient reaches the skin.
Conversion chain and clinical potency
The key conversion is from aldehyde to carboxylic acid, catalysed by aldehyde dehydrogenase (ALDH). This step is efficient in most skin types, which helps explain the faster action compared with standard retinol serums. The core reference here is Fluhr et al., 1999 (PMID 10416521), which compares different topical vitamin A derivatives.
- Retinal is converted into retinoic acid in the skin by aldehyde dehydrogenase enzymes in a single metabolic step.
- Efficient ALDH activity in most people explains why retinal often works faster than cosmetic-strength retinol.
- Local enzyme expression means each area of skin can regulate how much active retinoic acid is generated from retinal.
Retinal and acne: antibacterial activity
Retinal has demonstrated in vitro antibacterial activity against Propionibacterium acnes (now called Cutibacterium acnes) (Péchere et al., 1999). It works on two fronts: it normalises keratinisation and helps clear clogged pores, and it directly inhibits bacterial growth on the skin surface.
For comedonal or comedonal-inflammatory acne in adults, combining a retinal serum with niacinamide often gives visible improvement in inflammation within 2–3 weeks and better texture control by around 6–8 weeks. In my experience at the pharmacy counter, this direct antibacterial activity makes it more useful than retinol alone for this specific acne profile.
Profiles: who should use it — and who should not
You want to improve the look of fine lines, texture and firmness over time. Crystal Retinal 10, at 0.1%, is better suited to people who have already used retinol or retinal before and tolerate retinoids well.
If your skin tends to become red or reactive, start low and slow. Retinal 0.05–0.06% can be a more manageable entry point than stronger retinoid routines, especially when paired with niacinamide, hyaluronic acid and a barrier-supporting moisturiser.
Retinal can help support skin renewal, improve the look of clogged pores and make texture appear more refined. Start with 0.05–0.06% and build tolerance gradually.
Topical retinoids are usually avoided during pregnancy and when trying to conceive. During breastfeeding, avoid retinoid skincare unless your GP, midwife, pharmacist or dermatologist has specifically advised that it is suitable for you. Systemic retinoids are known to be high-risk in pregnancy, and the cosmetic approach is deliberately cautious.
If you have previously had urticaria, marked dermatitis or a confirmed allergic reaction after using retinol, retinal or tretinoin, avoid retinal unless a dermatologist advises otherwise. Look at alternatives such as stabilised vitamin C, niacinamide, azelaic acid or barrier-supporting ingredients.
Medik8 Crystal Retinal: which strength should you choose?
My advice: do not start too high. It is better to introduce retinal slowly and increase strength later than to start aggressively and abandon the routine because of irritation. Consistency is what makes retinoids useful in real life.
Step-by-step introduction protocol
Weeks 1–2: low and slow
Use Crystal Retinal 6 one night per week. Apply to dry skin — wait around 5 minutes after cleansing. Dose: a rice-grain amount for the face. If your skin feels tight, apply hyaluronic acid or a simple moisturiser before or after, depending on your tolerance.
Weeks 3–4: two nights per week
Increase to Monday and Thursday, keeping applications spaced apart. If significant redness, burning or peeling appears, go back to once weekly for another week before trying again.
Weeks 5–8: three nights per week
Use it on non-consecutive nights, for example Monday, Wednesday and Friday. On rest nights, use niacinamide, ceramides or a simple moisturiser to keep the skin barrier comfortable.
Week 9 onwards: maintenance
Use 3–4 nights per week if your skin tolerates it well. If you want to move up to Crystal Retinal 10, at 0.1%, introduce it slowly again over 2–3 weeks rather than switching at full frequency overnight.
Comparison table: Retinal (retinaldehyde)
| Molecule | Steps to retinoic acid | Relative efficiency | Tolerance |
|---|---|---|---|
| Retinyl palmitate | 3 enzymatic steps | 100% (reference) | Very good |
| Retinol | 2 enzymatic steps | ~150-200% | Good |
| Retinal (retinaldehyde) | 1 enzymatic step | ~2,200% (11× higher than retinol) | Excellent |
| Tretinoin (retinoic acid) | 0 steps (already active) | Maximum | Poor (prescription only) |
Frequently asked questions
Scientific references
