Depends on what you mean by proof. There are a few old keeper manuals around that recommend this as a treatment I remember reading this in some old AVS publications, as well as personal experience from many old time snake keepers, but you'll never find any clinical trials or anything like that. That kind of info just doesn't exist. No University or research facility is going to waste their time or grant money doing testing of this sort which benefits such a relatively small group of people.