I have an older gelding ( 22, Polish Arab )
that has an occasional cough, but is otherwise very healthy. The vet thinks it
is a dust allergy that gets annoyed at times. The dust in alfalfa hay can
bug him, or in general our Southern California dry dusty conditions. The vet
said we could wet his hay down, and the bedding in his stall if needed. He
is on a 2 acre dry pasture during the day with friends, and in a large stall and
attached large paddock during the night. He gives lessons and goes
on trail for a living. He eats about 70% bermuda & 30% alfalfa
hay. If the cough acts up for long periods of time I give him a cough product
for about 3 days to give him a break & he usually is a lot better after
that. Hope this helps !