I've had really good luck with Claritin - there is something that blooms around here in June that can knock me for a loop (the rest of the year isn't generally a problem).
I've not had any issues when using Claritin (and I'm fairly sensitive to that sort of thing in medications), although I'd try it on a couple of off-days before using it when you're going to be doing that pilot thing to see how it affects you.