There may be cross contamination, but is it possible you are reacting to something else in the food? My husband and I often have an odd reaction after eating out. Feeling like our throat is tight, coughing, headache, achy joints, unhappy bellies. I've also had hives this year, never had that before!
As a result we don't eat out very often. I do know restaurants get food sourced from places that may use preservatives, MSG and other things we normally would never take in. Add in not knowing if the other half of the tomato you got on your meal was rotten...