It creates scabby skin normally on the hind end, especially after damp weather as kim mentioned, but also if the horse hasn't been properly groomed in a while. My TB would get it, and I would just wash it with an antibacterial/anti fungal shampoo, and scrape all the scabs off so that the medicine could get down to the skin, and not just sit on top of the scabs. Now my Arabian wouldn't let me curry the scabs off, so I had to take a different route with her, and I just coated the entire area with MTG, would reapply it as needed for about a week, then wash it all off, and if needed do it again. She cleared up pretty nicely, then in my two week transition after losing my job, she got it again, and as soon as I got a bottle of my own MTG, started applying it, and within a couple of days it was all cleared up. A good grooming goes a long way, as does blanketing, and applying medicine as soon as you notice it. If you like her, and work well with her, I would not pass up on her just because she gets rain rot.