When you first start using Retin-A, apply it every other night or every 3rd night. The flaking and irritation side effects are usually the worst in the first 2 weeks of application. As your skin adjusts to the medicine, you can apply it more frequently. If you notice an increase in the irritation or flaking, it's ok to take a break for a couple of days. Just don't stop completely without consulting your health care provider!