My 10 month old Biewer Yorkie has been sick with vomiting and diarrhea for about 4 months now. He has it about 1-2 times weekly. He has had lab tests, stool, urine and ultrasound. All normal. I have always felt he gets sick after his application of Frontline but the vet told me it was impossible. He weighs 5 pounds. I dont mean to put down any product I am just so worried about him and would like to know if anyone else has a puppy who is so sick on some days and other days he is completley fine. He is on a prescription diet of Hills Science z/d diet. On his sick days he does not eat or drink all day and has vomiting and diarrhea. Help, I want to make him better and all of the vet visits and tests are not helping.