I am not a doctor or qualified in any other field of medicine. If not wearing fragrances on a particular day stops the migranes that day, it suggests to me a direct reaction from breathing them in (or possibly from having them on your skin) rather than any kind of slow build up. Maybe it is an alergic reaction? I don't know anything about migranes and how they are caused. Maybe if you experiment carefully you can find particular frags which don't cause the reaction (maybe it is particlar ingredients, maybe try some completely natural and some completely synthetic) but at the end of the day if it is affecting your life so much maybe its best just to stop wearing them. I really enjoy fragrance but wouldn't put up with this sort of trouble for them. Good luck with this.