Since then, he has gotten a cough that is pretty bad any time I ride. He also coughs when he's just hanging out, but not nearly as much. Except for that first day, he's still been happy and active in turn out and still has a healthy appetite.
I started him on AniHist, but it doesn't seem to have any effect, and his cough has gotten worse in the week and a half or so that he's been on it (but no more mucous that I've noticed).
Last Thursday I had the vet come look at him since I'm out of town this week and didn't want it to develop into something worse while I'm gone. His lungs sounded pretty clear, so nothing to worry about there just yet. She recommended soaking his hay and gave me some steroids to use if it doesn't get any better or continues getting worse. I also discussed using Cough Free, since the barn owner has some that she said I could use, and the vet said it couldn't hurt. So, I added that to his supplements as well.
My trainer will be riding my horse a couple times while I'm gone and will start the steroids if needed, however I'd prefer not to use them if I don't have to. So right now, the changes I've made are soaking his hay, AniHist, and Cough Free.
Assuming he's still coughing when I get back this weekend, I want to be prepared with something else to try. Does anyone have any recommendations on products that have worked for coughing caused by seasonal allergies? I'm hoping it will clear up on its own within the next month, but he's new to me, so I don't know how long it will last