Retinol.

"This is a paper in a very credible dermatology journal showing the efficacy of an over the counter retinol comparable to prescription tretinoin for improving the visible signs of skin aging. If you had asked me before this study what I recommended, I would have said there's nothing about it that makes me think it's any more convincing than the retinols I typically recommend. But now that we have this paper showing it gets into the skin, activates the markers of retinoid activity, and shows clinical improvement in the visible signs of photo aging, I can actually recommend this product as a retinol. I feel pretty confident that if you chose it you would at least be getting the benefits of a retinol, although it's got its limitations, since this was a very small study that only enrolled Caucasian skin types and didn't control for the vehicle. I'll also point out that a lot of the reason people pursue retinol over tretinoin is that tretinoin can be irritating, and I'm not completely convinced this is going to be less irritating for you, because the only difference found was less redness in the SkinMedica group. Dryness and peeling were comparable between the two. It costs about 80 dollars, and this study was funded by SkinMedica, which is worth considering as a potential source of bias, though I wouldn't chalk it all up to that given how rigorous the study design was."