Infections can be a culprit. So can stress. Some people get flares if they overdo activity. Others say certain foods trigger problems, though there's not a lot of research to back that up. The important thing is to find out what tends to bring on a flare. The next time you have one, make notes about what's going on in your life. For instance, what's your overall health like, what kind of activities do you do every day, and what kinds of food do you eat? Once you learn your triggers, you can take steps to avoid them.