Retinal (retinaldehyde): why it beats retinol and how to use it
What retinal is and how it differs from retinol
Retinal (retinaldehyde) is an intermediate metabolite of vitamin A, further along than retinol in the conversion cascade towards retinoic acid. It only needs one enzymatic conversion to become active; retinol needs two. That translates directly into speed and intensity of results.
In products such as Medik8 Crystal Retinal, retinaldehyde is stabilised to maintain its bioactivity and prevent premature oxidation. Oxidised retinal before it penetrates the skin is useless: that stabilisation is what separates a serum that works from one that does not.
Conversion pathway and clinical potency
The key conversion is from aldehyde to carboxylic acid, catalysed by aldehyde dehydrogenase (ALDH). This step is efficient in most skins, which explains the faster action compared with retinol. The core reference here is Fluhr et al., 1999 (PMID 10416521).
Retinal and acne: antibacterial activity
Retinal has demonstrated in vitro antibacterial activity against Propionibacterium acnes (Péchere et al., 1999). It works on two fronts: it normalises keratinisation and clears pores, and it directly inhibits bacterial growth.
For comedonal or comedonal–inflammatory acne in adults, combining retinal with niacinamide gives visible improvement in inflammation at around 2–3 weeks and texture control at 6–8 weeks. In my experience this direct antibacterial activity makes it outperform retinol alone in this profile.
Profiles: who should (and should not) use it
You want to reduce wrinkles and improve firmness within roughly 12 weeks. The 0.1% version is ideal if you have already used retinol.
If you are prone to redness, a retinal at 0.05–0.06% tends to be better tolerated than retinol. Combine it with niacinamide and hyaluronic acid for maximum comfort.
Pore normalisation, sebum control and antibacterial activity in a single step. Start at 0.05–0.06%.
All retinoids should be avoided during pregnancy and breastfeeding. Systemic retinoids are teratogenic. Even though topical absorption is minimal, caution is essential.
If you have had urticaria or dermatitis with retinol or tretinoin, avoid retinal as well. Retinoid allergies are usually class-specific. Opt for stabilised vitamin C or niacinamide instead.
Medik8 Crystal Retinal: which one to choose
My advice: always start with the 0.06%. It is better to introduce it slowly and step up than to start strong and give up because of irritation. Sticking with treatment is what really delivers anti-ageing results.
Step-by-step introduction protocol
Weeks 1–2: “Low and slow”
Use Crystal Retinal 6 one night per week. Apply on dry skin (wait around 5 minutes after cleansing). Dose: about a grain-of-rice size amount. If you notice tightness, layer a hyaluronic acid serum beforehand.
Weeks 3–4: two nights per week
Increase to Monday and Thursday, always spaced apart. If you develop marked redness, drop back to one night for another week.
Weeks 5–8: three nights per week
Monday, Wednesday, Friday (non-consecutive). On rest days use niacinamide or ceramides to support the skin barrier.
Week 9+: maintenance
Use it three to four nights per week long term. If you want more efficacy, switch to Crystal Retinal 10 (0.1%) and introduce it just as slowly over about 2–3 weeks.
Tabla comparativa: Retinal (retinaldehído)
| 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) |
Preguntas frecuentes
Referencias científicas
