Retinaldehyde
In plain terms
A vitamin A derivative that skin converts to its active retinoid form in a single step, which makes it stronger than retinol and still gentler than prescription retinoic acid. It works for aging and acne, and like every retinoid the line to watch is pregnancy.
What the evidence shows
Retinaldehyde is vitamin A in its aldehyde form, one metabolic step from retinoic acid, the molecule that drives retinoid results. That single step makes it stronger than retinol while staying better tolerated than prescription retinoic acid: in tolerability testing retinaldehyde and retinol sat at the same low level of irritation, because skin converts only a small share of it to tretinoin and stores the rest. A controlled trial found retinaldehyde creams at 0.05% and 0.1% effective on photoaged skin and well tolerated. The consideration that carries the verdict is pregnancy. Retinoids taken into the body are a documented cause of birth defects, and although topical retinoids are absorbed only slightly, dermatology guidance and European regulators treat the whole retinoid class as one to set aside during pregnancy, and the EU classifies retinol and its esters as able to harm the unborn child. Europe capped those esters and retinol at 0.3% in 2024 and added an intake-reminder label, but it left retinaldehyde outside that cap, and the US sets no limit either, so there is no strength printed on the label to read. For a non-pregnant adult, retinaldehyde is effective and, at the low strengths sold, usually easy to tolerate; the sensible approach is to start low and build up, and to set it aside entirely while pregnant or trying to be.
On the label
Listed as retinaldehyde or retinal. If you are pregnant or trying to be, this is the retinoid to set aside; otherwise, since no cap means the strength is not something you can read off the label, start with a low percentage and use it a few nights a week before building up.