Battles Gentian Violet spray has saved me on many occasions in the past. If my horses get mud fever it is my go to product and has been for several years. I am lucky that my horses have a pretty strong constitution but this winter has been hideous with them standing in water for months. My youngster got mud fever which was pretty persistent. Battles Gentian violet spray knocked it on the head within a few days. Because it isn't a cream base it can get sprayed on even if their legs are wet and muddy, they rock the purple look for a few days but it sorts it out with very little hassle. I recommend it all the time.
One of my Chooks was struggling with a soft egg and set upon by the others which left her with a nasty wound under her vent. After a few days of cleaning up with salt water etc, and remembering Gentian Violet from my childhood days of bringing neutered purple cats home from the vet - I decided to treat her with it and now she is walking tall again, not afraid of getting pecked!
(agree with the Purple hand comments.. wish had read the reviews before applying!!)
I got this as 3 of my chooks have had the feathers pulled out from their bottoms and it was starting to look rather red and raw. I sprayed this on them and it seemed to halt the pecking getting any worse. However my white sussex's now have very purple feathers all round their bums! Better this than bleeding wounds though. ( Do use gloves when applying as it will stain your skin for a few days)
This is good stuff and I would reccommend.