Hey everyone, I have an issue with one of my mares, Nacara. She's a black Canadian and has quite sensitive skin, and recently developed a severe rash on her withers/back, along her spine. She has raised bumps in this area that are EXTREMELY itchy, and when I rub her on this rash, her hair comes out. She has a tree stump which her and the other horses like to rub on, and she has rubbed her skin absolutely raw in certain areas, to the point where she has open, weeping wounds. We have absolutely no idea what's causing this and I want to know if anyone else has had the same issue????