What are the reasons for a pimple breakout? I never had a pimple problem, but recently I have been having a breakout on both cheeks, more so on the left one. It is not severe, but one pimple appears, then goes down, then another appears, and so on. I earlier used Himalaya acne-pimple cream which was effective in controlling pimples, but as the problem did not go away, I am using Tretin 0.05% every alternate day. How long should I continue?