"How allergic?" sounds like a sensible question,, however it is actually kind of impossible to answer. Food allergies are variable. An allergen that has caused mild reactions in the past may cause severe reactions in the future. "Red sneakers for Oakley" tells the story of a child who died from an allergic reaction to food when previous reactions had been mild. Asking "How allergic?" may make some people very nervous indeed.

I usually offer this kind of info in the form of “avocado mustn’t go anywhere near my plate, coconut there’s no fear with cross contamination but if it’s actually in my food I will be sick” (I have an actual allergy to avocado but coconut just upsets my tummy mostly). I don’t want someone cleaning down a whole area if a trace of it won’t do any significant harm and I think it then emphasises the importance of the ones that are actual allergies.

Just a note on letting people know your allergies even if you can’t see anything on the menu that looks concerning- I recently visited a cocktail bar that had straws made from avocado (which I’m allergic to) - I never could have known that if I hadn’t mentioned my allergies

i'm a chef & we get checks with 'no onions' etc through all the time and have to go back & ask if it's an allergy or preference, because if the latter, they probably don't mind things cooked in veg stock (which contains onions, garlic, leeks etc) and most likely just don't like the taste/texture of actual onions; if it's an allergy, we need to know to avoid those things. i'd declare any allergies no matter what, so the kitchen knows to be extra aware of cross-contamination

Thank you for caring so much, seriously!