I think it's probably just the irritation from it.  It takes 30-90 days to really see a difference in fine lines due to an increase in collagen.  There may not be much benefit from using the higher concentrations of tretinoin (Retin A/Renova) over the long term. Since it causes more irritation, I generally advise my patients to stick with the 0.025 or 0.20% because they will use it more consistently.  Dr. I