The absurd thing to me is that e.g. an ice cream place asks if dairy is OK. We all know ice cream contains dairy by default. If you are allergic, you know. It's a pretty surreal way to be considerate.

(If you're allergic to something more exotic, you also know to not blindly trust the reassurances of people who, while good natured and friendly, never had reason to learn the fine points of allergy stuff.)

Also, people don't generally identify with their allergies, it's not like acknowledging the existence of allergic people in a redundant way validates them or something. A sign notifying that milk-free options are available is plenty.