Hi Anne,
I've been a writer of canine health care issues for a couple of decades. Allergies and diet are hot button topics so I'll keep my comments short and send you a link to further reading. My basic
answer is to try and get the animals back to a more old-fashioned lifestyle.
"We" (meaning permies-type
people) make sure our chickens are not eating GMO. We make sure our cows are grass fed. We make sure *we're* eating right. But so many still feed the dogs processed foods, vaccinate excessively, and load the dogs with chemicals. It's what we've been taught to do, to be good dog owners. We want to be good dog owners so we follow these recommendations.
Lighten the dogs load of irritants and you might see a reduction in allergies. We sure noticed that in our first Dachshund.
http://puppies.petcarebooks.com/natural-rearing/ Good luck. Keep cool this hot summer.
Best,
Caroline