The worst ones would last three weeks and seemed to be triggered by stress. At the time, my diagnosis was lupus (perhaps a part of MCTD—I’m not a medical professional). Lupus is known for these ulcers, I understand. I always used Biotene toothpaste and mouthwash as well as many tubes of an oral analgesic. I think it was orabase. The best one contained tannin but it stopped being available. I began drinking a lot of tea that contains tannin. Stress was a constant in the work I did and I also became caregiver for my 86+ year old mother who lived until almost 94, and later my husband. As the symptoms of my autoimmune disease morphed into RA and OA, the mouth ulcers receded in frequency. These illnesses are so complex. My husband and I have had several different dermatologists ; as you know, some physicians are more knowledgeable or dedicated and seem to have more resources for information. I would encourage your grandson to seek another opinion—preferably Mayo if at all possible. The communication among physicians in different practices often falls by the wayside, I’ve discovered. Dermatology and rheumatology are tough fields and often seem to have no solid answers. Please don’t give up hope for successful treatment.