In any case, I think the underlying statement (the one I originally challenged, quoted below) is false, on two levels.
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It appears there are mechanisms by which exposure to smoke or other non-protein-based substances can result in an allergic outbreak.
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(Off topic for this thread, but not the hijack to the other one) Regardless of the precise mechanism, or even the precise type of reaction, responding to the question “may I expose you to chemical X?” with “Please don’t - I’m allergic” is still a sensible and reasonable response.
The waiter does not need to understand or care that your aversity to shellfish is actually because of an intolerance. The person offering you a glass of sulphited wine does not need to know or care that the sulphite releases Sulphur Dioxide, which is then a factor in a chain of events, leading to anaphylaxis. “No thanks - I’m allergic to it” is probably the right thing to say.