Tretinoin
"I'm a young woman in my early twenties with moderate acne.  If you're just starting Retin-A, STICK WITH IT  I started using Retin-A (0.01%) every night in December of 2013.  I was very frustrated because my acne became worse for about 2 months.  However, I stuck with it and by July 2014 my acne had noticeably decreased.  It is now October 2014 and I've been getting compliments on how great my skin looks!  For the first time in years, I don't feel like I have to wear liquid foundation to cover up my acne. If you experience flaking, remember that moisturization is key if you're using Retin-A!"