I know you have to wait a few weeks in between derma rolling sessions on your face. But what I want to know is, can you derma roll different body parts at the same time? For example, if I want to derma roll my face and chest, would doing both at the same time cause any problems or lessen the affect if I hadn't done them at the same time? If I can't do them at the same time, then how do you derma roll multiple parts of the body without lessening the benefits?