I'm on day 24, and so far my hayfever and other allergies seem to be far less. I used to go out for a walk at this time of year, get back, and about an hour later my eyes would be red, swolen and watering, my sinuses would be blocked up. So far, none of that has happened. I guess its possible that theres less pollen about though.
I'm allergic to dust too and haven't noticed anything more than a slight tingle in the nose when I'm exposed to it.
I can't speak for allergies to cats as I'm not allergic to them, but its certainly worth a go.