I was at my vet for an unrelated issue. He happened to mention a dog which he had a difficult time diagnosing. Symptoms almost exactly like what you are mentioning. They finally figured out the dog was allergic to a specific type of grass! When the grass was growing and some turning to seed, it was much worse. His client killed all that type of grass and reseeded and it worked.

I have one dog with similar symptoms and I think it's from mold spores. Was it exceptionally rainy when the dog was so bad? I recently realized that my dog is itchy after prolonged rain so that pointed me to mold spores. My area is getting a lot of rain this year. I get pollen reports emailed to me and there never was a correlation to symptoms and pollen. Some areas of the country will report mold spore counts but not where I live. The dog may smell the microscopic mold in the grass and wants to stay away.

My vet is stumped too and a vet tech thought it was the type of grass I have, I don't buy it. I only have a problem during the rainy part of the year and not every year. I haven't run this buy my vet yet but when it drys up I should get my answer. For now I've changed my air filter on my AC/furnace air cleaner and I've increased ventilation in the crawlspace under my house. I plan on doing more to my crawlspace. You don't have to have visible mold to experience the effects from it and people are affected too. I might have an answer to my seasonal congestion as well.

We did several skin scrapings, negative, we treated for mites anyway. Tried antihistamines, two types so far, they have no effect. Also doing the fish oil but haven't noticed any changes there yet. We changed foods to a limited ingredient diet because the symptoms started a little while after I switched foods but I think that's a coincidence because we've had this before. It seems like we'll never dry out over here, it rains almost daily. Unusually wet for us.

Thank you both for your replies, I will pass them on to the owner. It has been extremely wet this year, I can't remember what last year was like

Exact same thing last year. Ran allergy panel. Allergic to grass. Go figure.

Just went through something VERY similar!! Allergy tested for both food and environmental. He came back highly positive for potato. POTATO! The most common ingredient in nearly every "allergy" dog food. He also had a few other food items and the rest were some weeds, cedar trees, birch trees, dust mites.
We switched his food and his coat came back 100 times better. He is now dosed down on his pred, maybe .5 ever other day to every three days and taking allergy shots.
The hardest part was finding a food but his breeder recommended Canine Caviar Chicken and Millet and I now have two dogs in my house on it and both doing SUPER.

Yes, we also had beet pulp, which is in many foods. We use Orijen and Acana foods and life is normal again.