Ah, I'd never heard of it before today until I was viewing another thread. It's just that my friends pony has got a rash just above her coronery band and she has white legs. I just wondered if it could be buttercups?
does this help....
Buttercup (Ranunculaceae family) Frequently found in horse grazed pasture. Buttercups are potentially poisonous because they contain a compound called protoanemonin, which is a powerful irritant, causing inflammation or ulceration of the mouth, often with sorenes, increased salivation and sometimes colic. However this usually causes the horse to stop eating which makes this condition self-limiting, although it is always advisable to contact your vet if you are concerned.
When I was a kid the little grey pony I used to ride would get scabs/rash on his fetlocks in the summer. It was always referred to as Buttercup fever (i.e. Mud fever, but caused by pollen). A good covering of Protocon Cream used to clear it up.
My TBX gets ulcers on the lips every year about this time, coinciding with buttercups coming out. We don't have that many buttercups either! The ulcers heal nicely on their own after a couple of weeks, (used to use Dermobion on them until we ran out of it and obviously now its no longer available) but we do avoid putting a bit in his mouth while the ulcers are present (I think he enjoys his annual holiday). I have noticed, however, that each year the ulcers seem to be slightly less bad than the previous year, so I've been wondering if he's over time building up a bit of resistance. My other 4 horses have always remained completely unaffected, yet are all turned out on the exact same pasture.