I give Rosie benadryl occasionally for allergies. My vet only suggests childrens liquid. I am not sure why. But this is the same vet that says no to Zyrtec while other vets say it is ok. The problem is they tell me that Benadryl has a very short lasting effect. As a last resort, he will give a shot for allergies. You might try a limited ingredient diet if it is allergies. Believe it or not, Rosie has allergies toward grass. Lol. I am the only person in the world to get a dog allergic to grass.
Another problem we have had is chiggers. Yes, dogs can get chigger bites. Good luck in solving the problem. Let us know how it goes. And welcome to YorkieTalk!