Does cat food hurt dogs and does dog food hurt cats?

My husbands dad is staying over while his fiancee is out of town and he brought his cat with him. Well with his cat he brought cat food and my dog seemingly likes the cat food more than her dog food and the cat seems to like the dog food more than the cat food. I expect my husbands dad and the cat to be gone by monday. My dog will only eat the cat food right now and the cat goes either way. Will this hurt either one of them if its only for a short while? Thanks in advance for answers/opinions!