"There's Daves on the starboard bow, starboard bow..."
 DB>    My horse has a cough that won't go away. His left nostril runs, his
 DB> nose sounds stuffed up, his breathing is labored at rest. He has no
 DB> fever, eats good, weight is a little low but good. His energy level
 DB> fluctuates. We are in Western WA.
We've had a few like that.
 DB>    This is Very frustrating. I have taken him to 3 Vets and the Tacoma
 DB> Equine Hosptal. They all seem to think it might be allergy/Heaves and
 DB> have treated him with Sulfa ,antihistimenes and Steroids. It helps a
 DB> little, but he goes right back after treatment. I have changed his
 DB> feed between grass hay,timothy,and alfalfa. They have low dust,no mold
 DB> and we have tried wetting it down. I have put him in different fields,
 DB> locked him in and out of the stable,and changed the bedding type.
That would've been my #1 guess too.
 DB>    If anyone has any suggestions, please write. I am running out of
 DB> ideas and money.
One thing you don't mention what bedding - is he on straw? Wood shavings
are better for allergenic horses, and peat's even better. Neither are
as much fun to muck out, and peat's expensive (might not even be
available where you are) but it might be worth a try. 
He could have hay fever, but it sounds like you've considered that 
already. Is he better when he's out for the day?
Simon
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