I don't have any food allergies, and I love peanut butter. Nobody in my circle has such an allergy.
However, in a different life I worked with nursing moms, and that is how I learned a lot about allergies. Most of the time, nursing moms can eat anything they want, but there are some babies born severely allergic to various foods -- usually cows milk (don't confuse Cow's Milk Protein Allergy to lactation intolerance -- two different things) but sometimes nuts or other things. As it turns out, some people who are extremely allergic CAN DIE just from the tiny bit of allergen that's floating around an enclosed space. They do not have to eat it or touch it themselves.
Feeding the child the food in question at an early age is not a sure cure -- some babies react very strongly from birth. (Some doctors think this very notion is false. I don't know.) An epipen is NOT enough to save your life if you're having a severe reaction -- it's meant to buy time until you can get to an ER. Some people will require many doses to survive. So that airline employee who flippantly made that remark should be set straight.
These people don't have allergies in order to make your day bad. They didn't ask for them, and their parents didn't cause them. I don't want anyone to die just because I like peanut butter. Nor do I want the plane to have to turn around while we watch someone go into anaphylactic shock -- I hope to never see such a thing. It's reasonable for a restaurant to post a warning that they do have peanuts on premises, and for an allergic person to refrain from going there. But are we prepared to tell allergic folks they just can't ever fly? What if there's an allergy specialist they want to see across the country or on another continent?
One more thing: Sometimes people become allergic quite suddenly for no apparent reason. I might have developed an allergy to concord grapes, because the last time I ate them, my lips became weirdly numb. Fortunately, that particular food is easy to avoid and I intend not to eat them again, just in case. But what if it were a more common food? Any one of us might develop an allergy to something common, like peanuts, and I think we'd all be singing another tune if we were told, "Well, no more travel for you, then!"
