I used to have it when I lived in one part of the city but the day I moved it stopped and has never returned. It was obviously environmental. It can’t have been furnishings because I took everything with me. I was convinced it was in the house too.
Was also convinced it was dust mites too. We fucked off every carpet and went wood and tile.
I know someone with a kid who had perma asthma too then moved and it also cleared up. Does it follow you on holidays?