I first started retin a August 2015 and stopped February 2016 because I never saw any improvement just more PIH and more severe acne. My dermatologist isn't the best, he just prescribes me things and doesn't really tells me how it works but he recently recommended I go back on retin a so i did about a week ago. I now realize how incorrectly I was using retin a the first time and I'm hoping because I'm using it correctly this time around it will make a change.