Retinal is one step closer than retinol

The whole family is one molecule, at different distances

There is only one retinoid that actually does the work, and it is retinoic acid. Everything else you can buy is a form of vitamin A that your skin has to convert, or a synthetic molecule built to fit the same receptor. The number of conversions between the bottle and the working form is the single most useful thing to know about any of them.

Each conversion costs something. Some of what you applied never makes it to the next rung: it gets stored, or shed with the surface, or simply never converted. That is why a retinyl ester at the same percentage as retinal is not the same treatment, and it is also why the gentler forms are gentler. Less arrives.

And a conversion is a smaller thing than it sounds. The four forms are the same molecule with one corner rewritten: an ester carries a fatty tail, retinol an alcohol, retinal an aldehyde, and retinoic acid a carboxylic acid. Everything else, the ring and the long chain that does the actual work at the receptor, is identical in all four.

3D scenewalk the four ends, one station at a time

What that means for retinol against retinal

Retinal sits one rung below retinol, so it arrives at the working form having lost one conversion less. That is a real difference and it is a mechanical one. What it is not is a measured statement about results, and this is where most of what you will read goes wrong.

Our own knowledge base scores Retinol and Retinal at 9 and 9 out of 10 on efficacy. The same number. Where they separate is on the two things a person actually feels and can check: Retinal carries the moderate irritation rating against high for Retinol, and Retinol has the longer research record, strong against moderate.

So the honest summary is that retinal is the closer one and the kinder one, and retinol is the better documented one. If somebody tells you retinal is a multiple of retinol at the same percentage, ask what was measured. We could not find it, so we do not print it.

All 10, drawn at one scale

The same ladder, with every retinoid our glossary holds and each molecule drawn from the same structure file its 3D scene uses, at one shared scale. Retinyl palmitate is drawn longest because it is longest: it is retinol with a sixteen-carbon tail bolted on, and that tail is the first thing the skin has to take off again.

5 of them are vitamin A forms your skin has to work on. 3 skip the ladder altogether: tretinoin already is retinoic acid, and adapalene and tazarotene are synthetic molecules that act at the same receptor without being vitamin A at all. All three are prescription or pharmacy products in most countries, which is the trade for having no conversion to lose.

The 2 we could not place

Two of the 10 have no step count on this page, and they are the two whose route is stated most confidently everywhere else.

• Retinyl Retinoate. A hybrid of retinol and retinoic acid. It has wrinkle trials behind it and no published route.
• Hydroxypinacolone Retinoate. Sold as needing no conversion. We could find no study measuring what the skin does with it.

We looked. There are clinical trials on retinyl retinoate with wrinkle endpoints, and there is a supplier literature for hydroxypinacolone retinoate that asserts it binds the receptor directly. What we could not find, in either case, is a study measuring what skin actually does with the molecule. So the column says not known, which is a worse-looking answer and the only one we can stand behind.

Which of these you can actually buy

From our own product decodes: 16 of the products we have taken apart carry a retinoid, and they cluster on three rungs of the ladder.

• Differin Adapalene Gel 0.1%Adapalene · 0 steps to active
• Medik8 Crystal Retinal 6Retinal · 1 step to active
• Geek & Gorgeous A-Game 10Retinal · 1 step to active
• Celimax The Vita A Retinal Shot Tightening BoosterRetinal · 1 step to active
• The Ordinary Retinal 0.2% EmulsionRetinal · 1 step to active
• Beauty of Joseon Revive Eye Serum: Ginseng + RetinalRetinal · 1 step to active
• The Ordinary Retinol 0.5% in SqualaneRetinol · 2 steps to active
• CeraVe Resurfacing Retinol SerumRetinol · 2 steps to active
• The Ordinary Granactive Retinoid 2% EmulsionRetinol and Hydroxypinacolone Retinoate · 2 steps to active
• Paula's Choice Clinical 0.3% Retinol + 2% Bakuchiol TreatmentRetinol · 2 steps to active
• CeraVe Skin Renewing Retinol SerumRetinol · 2 steps to active
• The Ordinary Retinol 1% in SqualaneRetinol · 2 steps to active
• Neutrogena Rapid Wrinkle Repair Retinol Renewal SerumRetinol · 2 steps to active
• La Roche-Posay Redermic Retinol B3 SerumRetinol · 2 steps to active
• OLAY Regenerist Retinol 24 Night MoisturizerRetinol and Retinyl Propionate · 2 steps to active
• The Ordinary Granactive Retinoid 5% in SqualaneHydroxypinacolone Retinoate · route not established