Most of the things you will use self-hypnosis for are not strictly medical consdtions, though some may indirectly affect your health. Stress is the most notable of these.
For pain or other medical conditions, it is important that you see a medical professional who can give you an accurate diagnosis. For most acute conditions, medical intervention will be all you need. For some chronic conditions, you may choose to use self-hypnosis instead of drugs or other treatment, or if the drugs don't work for you.
For instance, arthritis causes chronic pain which is often treated with drugs. Pain relief is one of the major uses for hypnosis, going back many years. So someone with arthritis could use self-hypnosis, either with or without drugs, to relieve the pain. The important thing is to see the doctor first to get a diagnosis so you know the real cause of the pain and if it requires intervention other than hypnosis.
One of the very few dangers of self-hypnosis would be in self-diagnosing pain or other symptoms, and deciding to use self-hypnosis instead of medical care. This could result in not getting treatment for a treatable disease, and that could be dangerous.
So if you're feeling poorly, go to the doc. Get the physical therapy, take the antibiotics, or give up your appendix if necessary. But if they can't fix what's ailing you, talk to your doctor about you relieving some symptoms with self-hypnosis.
