The Peter Gurney Guinea Pig Pages - Skin problems.
You can try this site. It's kinda hard to understand, but what I take from it is you apply it directly to the skin that is affected. But, I don't feel comfortable telling you "Yes, it's OK if they swallow it", because i'm not too sure. All I can say is to research other sites as well and maybe someone on here has personally tried it and they can tell you more. Hope the link works. Good Luck.