My old gelding had terribly sensitive skin and got scratches and rain rot really, really easily ( he also had copd and was regularly on steroids so it may have been an immune system issue). Anyways, after many years and many products and home remedies the ONLY thing that worked 100% to clear up his skin problems was MTG.
I've used it on many horses since and never had any bad reactions. It smells absolutely awful, but it works! I love MTG.