Do a search on this forum under 'hayfever'
This comes up every year and there are a few if not plenty of accepted medicines/tablets approved for use by commercial pilots.
I suffer myself but I only fly PPL, If it gets really bad I get a steroid injection in my ass
which is fantastic and last for about 6-8 weeks and completely clears any symptoms. I'm not sure if its approved by CAA though.
Sneezing and rubbing your eyes on short finals in a crosswind could be tricky!
Cheers