Foaming at the Mouth

I saw this on one of my email lists, from Louise in Israel:

While you're at it, you can do the wild-animals-foaming-at-the-mouth "trick"- it's the old volcano using baking soda and vinegar, except that you mix together baking soda, citric acid (powder) and powdered sugar (to make it a bit palatable). Add a tiny bit of food colouring and put a teaspoon of it inthe mouth. The saliva in the mouth causes the reaction, and of course youdon't want to swallow this (not that it'll harm you if you do however), soyou just foam at the mouth, in whatever colour you chose. Messy, but fun.

So, being the total fool that I am, I tried it:

Thank you to my friend Christine for being willing to photograph my more glamourous moments. (Anyone have Katie Couric's Photoshop editor to work on my facial lines?)

And my adventurous Lauren also tried it:

I'm not quite sure what learning we accomplished, but we did have fun.