My dog has been hacking and wheezing for months due to allergies - what can I do?

We have a couple of dogs at our clinic that are on an allergy medication protocol. They get a shot from one vial, a week later they get a shot from another vial and on the third week a shot from the last vial. Each vial contains a different medication and the regimen is started again once the symptoms return. They come in every couple of months or so to get the shots. That may be something your vet could look into.