I have been having olfactory hallucinations for about 3 years now. They last a few minutes, occur 1-2 times a month, and the smell is not unpleasant, a sort of chemical smoky smell. It is very characteristic and now I recognize it right away as an hallucination. (In the beginning I thought my neighbor was smoking something funny). I don't have migranes, but I have had 2 or 3 visual migranes in which there was a blurry line that stretched diagonally across my field of vision. I wonder if these olfactory hallucinations could be related to the visual migranes or if they may be related to a bike accident I had 6 years ago in which I had a concussion in which I was unconscious for ~15 minutes.
Thanks for your response!