I had a chick that liked to dunk her beak/face in the water, then she'd sneeze like crazy. She finally quit doing it after a week or so, and now they all just sneeze on occasion. No runny noses or any other symptoms (I kept a close watch) so I decided to quit worrying about it.
Easier said than done, I know! I often have a lot of trouble with allergies, so I am not surprised that my chickens might have some trouble, too.