Hi Cary,
Horses seem to respond well to Xue Fu Zhu Yu Tang, which has a good effect on moving Blood in the upper burner. This translates in part into improving circulation through the sinuses, which has the effect of reducing chronic inflammation, reducing fibrosis, and reducing monocyte infiltration. Improving circulation works by helping remove inflammatory infiltrates and improving vascularity following the ravages that acute congestion creates. It's the first thing I'd try, given how well horses tend to do on it.
Steve