Cachalot, I saw you at Otakon in costume. I wanted to flag you down and talk about how you did the makeup, but I was rushing to an event. I'm glad you picked PAX, and I'm glad it worked out as well as it did. The pics look fantastic.
I could be wrong, but I think I was the first person who started talking about using PAX in any detail on this site, years back.
Dust Bunny, the safety of PAX is a complicated issue. In the US, there are very stringent rules and regulations on toxicity of paint. For liquitex, and basically any paint you will find in a craft store, products are certified by ACMI to be labeled in accordance with the chronic hazard labeling standard, ASTM D 4236, and the U. S. Labeling of Hazardous Art Materials Act (LHAMA). They are generally rated CL and/or AP. You can find more details here: http://www.liquitex.com/healthsafety/generalhealth.cfm
Cosmetics are regulated by a different body in the US, namely the FDA. They have a specific list of chemicals that are considered safe to use in makeup. Among these chemicals, some of the pigments in the range of reds and purples have stipulation that they not be used on the mucous membranes (namely, close to the eyes). I spent a good deal of time researching this, and I've never been able to find a friendly statement explaining the situation.
Hollywood has been using PAX as a special effects cosmetic for about 40 years now. Granted, they are professionals, so they are able to assume greater risk. Many times when you buy stage makeup, you will see it labeled with "For Professional Use Only". This means that the product hasn't been evaluated using the same standards the FDA puts on retail cosmetics, and it's the responsibility of the person applying the product to see that it is used in a safe and proper manner.
In general, any makeup should be tested on the skin first (I like to use the skin just behind the underside of the wrist, as it is particularly sensitive). And if makeup seems to be causing irritation, it should be removed quickly using the most gentle method possible.