I am sure someone has suggested this before, but just in case, I will mention it.
Many allergies in dogs can be started because of many of the ingredients in commercial dog food. Vets will suggest “hypo-allergenic” dog food, switching from chicken based to lamb based, etc.
Have you ever researched the raw meaty bone diet? I suggest you google Tom Lonsdale, and read up.
I have two Belgian Malinois who have been fed raw ever since puppyhood. They are now 9 and 10 years old, and have never been to the vet for anything except their puppy shots, and then rabies every three years. We live in the woods, with deer and other wild life all around. I have never used anything on them for fleas or ticks, and they have never had any trouble.
Healthy dogs can deal with these, but dogs fed commercial dog food are getting way more grains and starches than they can properly digest, and are not getting the raw enzymes and nutrients found in raw meaty non-weight bearing bones, organs, etc.
The money spent on the meat have saved us so much in vet bills. Our dogs have never had to have their teeth cleaned, either. Calculate how much that is over the years!
Also, our dogs are never bathed. Their breath is sweet and fresh, their coats do not smell, even when they have been in the farm pond, and their poop crumbles away to a white powder after a day or so. Neither do I have to express their anal glands, since the stool is much firmer than that on dog food, and does the job naturally.
Just something for you to think about while you research Tom Lonsdale’s approach to proper feeding of canines.