Hi and welcome to both you and Bart!!
I would definitely do as has already been suggested and get a second opinion. I don't mean to say that your vet doesn't know what their talking about but both allergies and symptoms of collaped trachea do not normally show up in a puupy. Neither of those conditions manifest until a dog is much older. I think it could be reverse sneezing which I think all puppies do from to time. |