I'm wondering how the vet got to "allergies" from coughing and gagging? That's honestly NOT a typical symptom. And it usually isn't until about 2 years old that dogs *develop* allergies and certainly not at such a young age as a couple of months old.
A couple of questions:
1. how much benedryl are you giving? The dose *has* to be at least 1 mg/lb body weight -- that may sound like a lot because that means a 50 pound dog has to take TWO over the counter capsules at least twice a day.
Yes, it makes them tired -- but longer term they usually get past that. And for those of us humans who live with allergies you just kinda understand that sometimes that's the price you pay to be able to breathe. (I have to take Benedryl -- none of the non-sleepy ones do a thing for me).
There are several different antihistamines dogs can take. **IF IT IS** seasonal atopic (inhaled) allergies usually Benedryl will *help*. It likely won't completely alleviate it but it will help.
2. Some of the things you say don't sound like allergies. It sounds more like heart. And honestly I wouldn't jump to heartworm.
Heartworm IS a possible. HeartGuard uses ivermectin -- but it's dosed SO lightly at this point that it fails all over the place.
When they do the test -- make sure they don't just do a test for microfilaria - you MUST test for the adult heartworms at this point -- there might not be microfilaria but there might be adults.
3. I would specifically ask the vet to look at the heart. There IS such a thing as a "heart cough". It sounds markedly like lung congestion -- but it's caused by the heart not by the lungs. But it would be a big huge thing to rule out given that this occurs AFTER EXERCISE. It's not happening when he's necessarily just out in pollen -- but you're reporting after exercise it's worse
5. HOW do you "get" the vet to look? That's not a stupid question -- but it's not an easy answer depending on your personality.
Learning to talk to a vet and get results is no small task. Sometimes it's worse in rural areas -- sometimes it's worse with some vets than others.
One of my theories of life is that some vets become *vets* because they are interested in medicine, but they really aren't comfortable about people. SOOOOO they *assume* that if they become a vet they will just get to work with animals ... right?
Nope -- because it's the people who pay the bills.
So some vets adopt this "DON'T QUESTION ME" attitude. they want you to just believe whatever they tell you -- no questions asked.
So, you learn to massage the conversation. You learn not to directly confront a vet like that -- you don't challenge their knowledge -- you simply "ask" things. Sometimes you ask over and over -- sometimes you ask again and again. You **respectfully** say something like:
"Gee Dr. Schmuckatella -- *you* are the vet here, but I'm really trying to understand ... could you pretty please explain to me how this can be allergies? Doesn't dog inhaled allergies usually involve the skin -- at least partly? His ears aren't red, his eyes aren't red and irritated ... so why would it pick the mucus membranes of the throat and lungs rather than the typical ears/skin route? It's just weird -- it **always** seems like it's when he's done some physical activity -- sometimes right inside the house, sometimes in the middle of a walk. It seems sooooo related to activity, more than the season."
Then you talk about the antihistamine -- and that it really seems to have no effect at all. Whether he's on it or not -- no change.
SOMETIMES vets simply treat for the easiest thing first. I'm not saying "good vets" or "typical vets" -- I'm saying "sometimes". They may decide to trust the wisdom of another vet until they can prove to themselves something else -- they may particularly NOT want to seem to "doubt" the other vet (particularly in a small town, and they already know you left the other vet because you didn't like them -- but there may be tension between the two vets and he may not want to seem like he's doubting the other vet).
SOMETIMES they may simply **assume** the owner has to "keep it cheap" and it's a WHOLE lot easier to try to pawn it off on Benedryl than to suggest an expensive test (like heart tests can now be done in YOUR vet's office but they usually have to call in to a vet teaching hospitals cardiac lab.).
Some vets are just plain terrified to suggest an expensive test to you -- maybe they aren't experienced in heart stuff, maybe they are afraid anything expensive will be out of the question.
Sometimes, and I hate to say this, the vet just isn't very good and simply does a particular "rote" list of things one after another -- because it keeps you coming back -- and maybe the vet wants to buy themselves time to look and research someting (and they can keep charging you a visit this way) and then **later** they can ask for that test, or try something "else".
5. You may have to do a little self-diagnosis.
Antihistamine -- you have to give that ... somestimes for WEEKS ... before it really kicks inl
Why?
Dogs have a Jacobsen's Organ between their nose and the roof of their mouth. Only some species have a Jacobsen's Organ -- it's essentially a highly developed organ of scent ... it is hundreds and hundreds of feet of unbelievably *thin* membrane -- literally "folded" (sorta like the inside of an air filter on a car engine?? if that makes any sense?) -- but that means every breath of air he draws -- particularly if he lifts his head to 'sniff' -- has to pass thru that Jacobsen's organ.
It's pretty complicated (and this is why dogs can smell stuff we don't even know HAS an odor) but allergens can get *caught* in that organ -- and it can take quite a while for that to get TO the lungs -- so it can take the body a while to arm itself against allergens and deal with them,
So -- my point is giving an antihistaminte occasionally is pointless. Benedryl is only a 6 hour drug -- usually you have to give it three times a day in bad allergy seasons, and you have to give it for weeks to really give it a fair trial.
You have to give that 1 mg/lb body weight as a bare minimum -- the range is 1-2 mg/lb body weight (and a vet can and sometimes will go higher than that).
Interesting points:
A. You haven't said a WORD about paw licking. That's typically the hallmark or 'gold standard' of dog allergies. Because dog allergies are usually completely tied to the skin -- literalloy the histamines will cause a 'tingle' in their skin that is very like if you or I sit on our foot and it goes to sleep? That's typically how the dog's paws feel -- and typically they will LICK them.
That, more than any other single symptom, is the typical "allergy dog" symptom.
B. How do the whites of the eyes look? Clear and white - or red and watery (again -- that's another typical allergy symptom).
C. Look at the inside of the ears -- often allergy will show as red ears -- not always but frequently.
7. Vet school? Three hours away really isn't far. I *know* you are having a difficult pregnancy -- and you're probably the dog-oriented one. so it might have to wait until you deliver.
8. But bottom line -- you simply ASK the vet to check this or that. It's reasonable. You ARE the owner. You're the one who sees this dog every day. You're the one who sees it happen.
Have you ever even seen the vet look at the dog with a stethoscope? Has the vet listened TO the heart?
The next time you see a coughing fit CHECK THE GUMS -- do they get pale?
My favorite resource is Giffen & Carlson's "Dog Owners Home Veterinary Handbook" -- it has a list of "symptoms" right inside the front cover. So rather than bouncing from disease to disease (which is one of the reasons why ANY doctor -- vet or human -- **hates** people looking on the internet. Because you can fit almost anything into a list of symptoms.
Vets typically don't diagnose that way -- they go from symptoms TO the disease. Not looking at a disease and seeing if the symptoms fit.
I hope this didn't ramble to bad --