(Boy, did I just date myself with THAT title!) ;-)
Working on the assumption that Lance has allergies (which would also fit with the seasonal mane and tail rubbing), Rick had me start him on prednisolone last Sunday. That has had no discernible effect, so we're going to try a regime of dexamethasone (Azium) to see if that quiets his symptoms. If it does, we should be able to go back to the milder prednisolone to maintain him; if not, scoping Lance is probably our next step.
Yesterday evening we went to the arena for a short schooling session, and I noted that the sand is drying out. Avoiding the loose, shifty areas and allowing Lance to cough seriously limited our schooling options; it's time to hit the "trails" (hacking on the roads and fields accessible from home). This morning I had some unexpected free time, so I strapped on his Renegade boots