sulfa dip is not for all external infections. It should be used as a preventative, but there are some legions and infections that need a anitbiodics.
I had a RES with legions on his skin and they gave my Amniglyde (sp?). I had to inject it into shoulder area of my turtle. It would have taken too long to treat if I tried to administer the meds orally.
I would have never known to use that or even know where to get it.