Why is my dog shaking and itching?

I have a year old chihuahua and I am obviously gunna take him to the vet, I was wondering what could be the problem. He keeps shaking as if he is wet but he isn't and he does the shaking a lot threw out the day and he has like ruff dry fur around his neck and lower back that's flaky like dandruff. He itches a lot too. I dnt see any parasites