My Holland Lop...is he sick?

He sneezes a lot. The bedding has been sitting around for a few months so could it be dust? He has no signs of being sick except sneezing he eats and nothing about him has changed. I'm thinking its the dust what do you guys thing? the sneezing has gotten less. But he did get wetfrom the rain because he refuses to go in his wooden part of the hutch when it rains (he likes watching rain lol) and he did get wet but I took him in right away and dried him off and he's now been inside for two days. What do u guys think?