"Microbes" under black light?

Question

I'm looking to show students how microbes can be transmitted from person-to-person. There is a substance that can be applied to an object, and as the person handles the object and touches other things, a substance trail is left. The black light makes the trail glow (really embarrassing if you've been scratching certain areas). My question is, what is this activity called and where can I order it? I've already tried a couple places like 3B-Scientific, but no luck.

Answer 1

http://www.epartyunlimited.com/invisibleink.html