I went and looked at a gelding (12 yr old) his legs have something on it that I've never seen. The owner said he thought it was some type of allergy to something in the grass he only gets it during the summer.
Anyway it looks like he scratches it alot, but I didn't see him touch it. Its kind of thick and makes the hair stand up on end, I think its because of the build up. Once you really get to touching and looking at it, it looks like cradle cap. I washed him (wanted to see how he was with water) and was looking over the legs, its real rough feeling, you can fell it coming off if you really rub it. I think it might itch, but like I said I never seen him touch or rub it, but when I was scrubbing it with my hand he stood so still, like it felt so good. He has white legs and after I rinsed him he it looked very red and irritated where it had come off. It was mostly on his feet but he had some on his leg not as much, but not on his body. He has had the same pasture mate forever and he doesn't have this problem.