Our Chief Medical Officer, Dr. Courtney Rubin, and our Head of Chemistry, Lizzy Trelstad, weigh in on your most pressing skincare questions.
Dr. Courtney Rubin’s take:
There is no evidence that retinoids should go on last. Most dermatologists recommend that the most active ingredient in a PM routine should be applied to the skin first, so that it has maximal exposure to skin and increased penetration. For that reason, and as long as the retinol is well tolerated, it should be applied first after cleansing. However, for consumers who are having difficulty tolerating retinol (those who find retinol to cause irritation), consider applying retinol after your moisturizer. This will decrease the contact the retinol has with the skin and increase its tolerability. Another option would be to only use retinol every other night, or decrease the % concentration of retinol you are using.
Retinoids are effective on clean, dry skin, though I've seen more and more people apply their retinol on top of a ceramide moisturizer to help reduce irritation and help bolster collagen production. On top of this, some even put a final face oil or sleep mask.
When you layer skincare, you're not always automatically decreasing the efficacy of the top layered product, but you are essentially decreasing the time until actives can reach and work on/in the skin surface. It’s important to note this decrease is not always statistically significant (I haven't seen many studies on the rate of diffusion from formula to skin).