Perhaps you could buy a box of treats that are okay for him - lamb and rice are sometimes safe for itchy dogs, and give a bag pf biscuits to each grandparent for when Jasper's begging. Or, if he'll eat carrots, buy a bag of baby carrots for them each to keep around.

From what I have heard, a lot of dog allergies are due to grains, how long has he been on the food he's currently on? Limiting his food sources will do a lot to help eliminate his allergies - or at least pin down what they might be!

And I know you cannot answer this, but how come they make over-the-counter allergy medication for humans that doesn't cause liver damage in a life-shortening way, but cannot do it for dogs?

I think the suggestion of contacting his breeder is a good one - I know MY allergies are in a great part inherited, maybe his are, too.