I am a huge fan of Pyrahna. It works great but you have to spray them almost everyday. But I've noticed that the sparys I use to get that said they'd last up 7 days or so, never did. In fact they didn't last one day. I've used on 3 of my horses and my friend used it her show horses, and neither one of us had any problems with it. Just test on a small area and make sure they don't have a reaction to it. If they do just hose it off real good.
Awesome Miss Take- Storm- 15 yr APHA PHBA Mare
SS Catalena Doll- Claire- 2010 AQHA Filly