The thing is that you don't get the real effect of Benedryl if you only use it symptomatically and occasionally. Then you are just medicating a symptom, not really maintaining the allergies.
The dose is ultra important -- and YES it makes them sleepy -- but they do learn to deal with it. Longer term, they actually get used to taking it and it effects them less negatively.
You *have* to give at least that 1 mg/lb dose and give it regularly **at least** twice a day because the whole point is to help the body deal with the histamines/allergens as they **COME IN** the body - not just the ones to which the body is already reacting.
You may need to try a different antihistamine (Tavist, Claritin, Zyrtec - -there are tons of them that dogs can use -- ask your vet.)
Vets can prefer to treat food allergies. It's easier to control what goes in the dog's mouth than what goes in it's lungs. But it sounds to me like you've pretty well determined there IS an environmental factor. It may either be time to try some stuff on your own, and/or switch vets. If you don't like the service and results you're getting -- let that guide you.
I have had some of THE most monumental allergy dogs of all times. Not just food allergy, but environmental, flea allergy and contact allergy as well.
At this point I home cook. It's flatly easier. I can completely control ingredients, I can add what helps and subtract what doesn't. I *know* food isn't an issue. Period.
At this point probably the most successful thing I'm doing is homepathy. This isnt' just some new weirdo thing I'm trying -- I've found an excellent vet who specializes in homeopathy and we've had incredible success with it. AT this point, Billy doesn't even have to take Benedryl at all any more.
That is nothing short of astounding. Now, he takes several different allergy homeopathics -- but heck, there are no bad side effects and he's happy and healthier than he's ever been.
I'm not talking about "herbs" -- homeopathy is a completely different branch of alternative medicine. If you're interested, contact me and I'll share my knowledge. It's not 'convenient' -- you usually have to give them 3-4 times a day. You really need a vet (they are a particular type of holistic vet -- it is a completely different modality than many holistic vets practice) who is knowledgeable. The rewards are big tho.
You might even want to simply *try* some homeopathics. Hylands "Hives" is a good allergy formula. They also have a "Hayfever" formula --you can give BOTH of them and not hurt a thing. No 'side effects' with homeopathy -- no sleepiness. But you need to give probably 2 tablets of each 3-4 times a day.
Not in food, and not NEAR feeding. Either crush the pellets with the back of a spoon (don't touch them at all -- pour them into a folded piece of paper) and then just pour the powder in the dog's mouth (it absorbs into the mucus membranes of the mouth and tongue)
It's sweet -- my dogs will literally chew the tablets themselves. You just don't want them to just swallow them -- they should absorb in the mouth, not the stomach.
See if it helps. It's not expensive, and not going to clash with anything else. There are other brands (some better) but Hylands is typically easy to find in most any health store (like a store that sells vitamins, supplements and herbs).