Assuming you feed the right food...do you rely on diet or do you add vitamins?? Someone told me to add a tsp. of olive oil to the food for shine..your thoughts?? Both my dogs get groomed everyday (yeah, I have that kind of time..lol) Neither dog has dry skin and their coats seem to shine from the frequent brushing...just wondered if I could do more.........neither are given extra vitamins at this point. THANKS.