Agree with comments re making sure you really have true scratches. There is an immune system skin condition called leukocytoclastic vasculitis is which is often mis diagnosed as scratches. It usually affects the white non pigmented skin on your horse’s legs and is often made worse by sun. The cause is not understood and is usually treated by steroids. It becomes worse in the spring and summer because of the sun. If you scrub off the scabs you can cause secondary infections. UC Davis had an article about this in their Horse Report ( I think 2006) which is available on line at the UC Davis equine web page . If I can find the link I’ll post it. Good luck to you and thanks to everyone else for their postings.