I know I've seen a lot of threads about itchiness lately, but I could use some advice

. Sebastian has been itchy since he was about 4 months old. He's not itching constantly, but I do notice it on and off throughout the day. He's been on Advantix since I got him, and I don't see any signs of fleas. His eyes run a little bit. Do most Yorkie's eyes run? With all the threads about fleas lately, I've been a little freaked out about that...but I really don't think that's what it is. Could it be an allergy to his food? He's always been on Nature's Variety Chicken and Rice kibble. He doesn't have any intestinal problems...and always has very normal poo. I talked to my vet about it when it started and they didn't seem concerned and didn't have much advice to offer.