I've just read an article by Anders Eriksson, located here.
I don't know Anders Eriksson, but he makes some very good points I thought I should highlight for my readers.
If you can, know your face painter before hiring him or her for a party.
You do want someone who's good with kids, who can interact with them well, and who is neither bouncing off your walls nor standoffish. You want someone fun, but who can cotnrol the line and insist upon maintaining a "polite zone."
You want someone who's using the proper products; not just FDA-compliant face paints, but also glitters and shimmers. You want someone who is concerned for the safety of your child and your guests. Always ask!
And you want to see samples of your face painter's work. Unfortunately, there are an uncrupulous few who lift the photos of others' work off the Internet and advertise them as their own work. Most painters who are willing to misrepresent their work in this way can't live up to their promises; they don't deliver the work the advertise. Again, always ask! It's worth it!