I am allergic to my piggies and their hay which is just wondeful! I get the full works of sypmtoms - sneezing, itchy eyes, runny nose and even a skin rash from the hay if I'm not careful.
I take cetrizine antihistamines (they are the same as Zirtek but as they are non branded they cost less than a pound a pack) which help a lot.
I also use deionizers in the lounge where most of my pigs are and upstairs. I always thought they were a gimmick but I have tried them again this year and I think I have been a lot better.