My son, 14 years of age, was having continual nose bleeds, at least 3 a week, from Dec-May. They stopped, it seemed, almost as soon as school let out. He began Jiu Jitsu in June and the nose bleeds have begun again. The bleeds only occur in the left nostril and do not last long, however, they only occur during Jiu Jitsu practice. What could be the cause? What can we do to limit the bleeds?