For years, eating at most fast food restaurants including Subway, Burger King, etc. gives me asthma and coughing fits. I'm not into junk food but sometimes when traveling there aren't other options. My allergist doubted that it was an allergy, suggesting it was a vocal chord disorder or a swallowing issue but a video esophagram showed I had normal swallowing. It also didn't explain why only some foods caused the problem. The allergist asked for me to bring a food that caused the asthma/coughing on the next office visit, and eat it while there. I ate a Burger King hamburger in the office and had my usual reaction to it. He did spirometry tests which showed an asthmatic reaction that was bad enough to require a breathing treatment. He suggested it was a food additive but I've not had any luck in finding the culprit until a couple of days ago. I avoid fast food like the plague but sometimes regular restaurants will cause a reaction.
A few days ago while traveling with friends, they wanted to eat at Subway. I mentioned why I can't eat Subway food and one of my friends remembered reading an article about Subway's use of a nasty chemical in their bread, that they have since discontinued; azodicarbonamide. Out of curiosity, I ate at Subway and had no reaction! I did some googling and found this additive to be the common denominator in the foods that cause me to have asthma. Interesting that I don't have this reaction to food in New Zealand and azodicarbonamide is not used there. It is linked to asthma and allergies. Googling it has given me some conflicting info in that respiratory and asthma issues are caused in workers who inhale it rather than by eating it. I'll do some more checking as I am skeptical by nature, but I have too much personal 'evidence' for me to disregard this.
I'm posting this here, hoping it might help someone else.
https://en.wikipedia.org/wiki/Azodicarbonamide