I would prefer that the airline notify me in advance that a passenger has such a disability. In those cases, I would be able to get other snacks. I hate the person eating M&M peanuts and then have the person have an adverse reaction and blame it right or wrongly on me.

Imagine buying an overpriced coffee and then finding out that I cannot drink it.

Gas masks mean that the user cannot eat. If you get the military version, he or she might be able to drink.