[makeitdouble]

Could it have been an allergy to something other than dust ?

I have an allergy to a specific cleaning product ingredient for instance, although I never got to know what exactly. It was not something commonly used, I never triggered it by myself and only reacted when helping cleaning a friend's house decades ago.

My kid also seems to have it, but again it only ever happened once at a shop, and no allergy test raised it (other stuff were found though)

"dust" allergy is sometimes complicated.