Try benadryl. My vet told me it was absolutely fine to give them either a child's dose, or half an adult dose (children's is 12.5mg, adult 25). It should calm his allergies a bit without major allergy medicine from the doctor. Not sure if they do it with dogs, but both my cats (one waaay more than the other, Molly almost died, twice) are horribly allergic to...something, we don't know what, get sick the same time very year, unless he gives them an allergy shot- basically, cortisone. He said it's unpopular with some vets, but it's worked wonders for mine. We now go for our annual visit a few weeks before that time of year, and it seems to prevent the whole thing.