RetinA can be great for prepping the skin for a chemical peel as it exfoliates the outer, older layers of the the skin and stimulates collagen production. I often recommend to my peel patients that they use RetinA prior to chemical peeling to maximize the benefit of the peel. That being said, it also makes the skin more sensitive to the peel (or other similar treatments like laser) and so depending on the type/strength of the peel and the patient's skin, I will occasionally have the patient stop using RetinA anywhere from a few days to a few weeks prior to a peel. Chemical peeling should be done by a physician in the office to avoid any unnecessary permanent discoloration and/or scarring.
Web reference: http://www.barnettdermatology.com/treatments.php?id=13