You should not blow in your dogs face as he may bite you
or if he's stupid enough to put up with it he may just get very upset at the way you are treating him. I knew a right tw*t who had a horse, he used to blow smoke into her face and say 'look, she doesn't like that'.
You should not let your dog put his head out of the car window as (a) it could get hit by a passing car/bike/any other moving object and (b) it could get something in its eyes/ears/mouth which could cause an injury or infection.