My friend's adopted rat questions?

Well im not sure what u mean it may be hes allergic to the bedding or even the dog its best you try cheeper bedding with less fumes in it.and change his food cause that he can be alergic to.if he continues to sneeze out of his cage 5 minutes he is out and he is still sneezing he may have a deseas and call your vet and see what you or your friend needs to do.call and all pet vetrenary this can be a deseas that can lead to death.