Shereene IdrissBoard Certified Derm, Founder and Chief Nerd

YouTube Channel

30 Jan 2026 · 1 min

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A short educational monologue explaining differences between over-the-counter retinol, retinal, and prescription tretinoin. It describes the biochemical conversion steps in skin: retinol requires two conversions (to retinal then to tretinoin) before becoming active, retinal requires one, and prescription tretinoin is active on application; concluding that retinol is the gentlest of the three.

Chapters

So when you're thinking of a vitamin A, a retinoid into your routine at night, it's important to understand the type and the concentration. So if you had an X and a Y, what is the type and what is the concentration? Retinols over the counter, the ones you guys are used to hearing about, R, T I N O l have to get converted into a retinal right before it becomes active in its active form, which is a prescription called tretinoin. This is. Forget which one. This is particularly. These are not ads. Okay, Forget this. So imagine retinol gets converted to retinal which then gets converted into this. So if you're using a retinol, you need to have two steps of conversion before it becomes active in your skin. If you're using a retinal, it just needs one step of conversion before it gets active in your skin. And if you're using a prescription tretinoin, it is already active once you apply it to your skin. So the most gentle of these three is retinol.