I have the same sort or reactions if I am unexposed to them for a while.

For example, I grew up with dogs and never had a problem living in the same house. When I went off to school and visited them on my trips home I'd have an allergic reaction. Now that I have one of my own I never experience any problems. THe same thing for me with cats, If I stay a friends house for a week the first few days are miserable (coughing, sneezing, running nose) but by the time I leave I'm fine.

I think that each person takes a certain amount of time to get acclimated. Stay tough, I think it will eventually go away.