Now it looks like three of my girls have it. I've read thru all the reasons, and can't find one that explains it. Anyway, Thru all the reading I did, I am going to try Ichthammol, apparently it's the best drawing salve, and people use it too. It's also has fungicidal and bacteriocidal effects as well. I put a glob on a piece of gauze, put it under a foot, and taped around it. It draws out infection. Hope it works.