it happened to my mom with soy. A few years back she started getting rashes and bad migraines until we realized it was related to her consuming soy. We did a research and this happens to people who have had allergies all their lives, just not food allergies. Probably you had respiratory allergies (lots of sneezing and itchy nose), or skin (rashes, breaking up, etc.) and now these allergies have become food allergies.
stay away from the foods that cause it, take a mild antihistamine every night and don't go eating anything weird
