I have never heard of such a thing here, is it common over there?
Yes, it is. Not just Ragweed, but all sorts of other pollens give a lot of people Hell.
I don't suffer those allergies anymore. My neighbor, then my Dr., suggested I find some local
raw honey, that produced within 50 miles of where I lived, and have a tablespoon of it each day. Within a month I no longer suffered from any pollen allergies.
To the OP, I hope you get relief soon. I know how miserable it is.
Ed