One of my mares has had a rather persistent, clear drippy nose. Too drippy to be normal, but not bad enough to seem like a vet visit is needed. No cough, great appetite… It just drips. Especially if you exercise her.
Allergies? It certainly doesn’t seem like heaves. But it doesn’t seem to be resolving on its own either.
I would think viral infection but wouldn’t that go away in a week or two?