Writing notes on hands, arms, and even legs appears to be very common in high school and even beyond (re: Sarah Palin).
I could find no scientific research that indicates the skin is permeable to the ink found in regular pens. There have been several studies on the safety of India Ink which is used to mark mucosa in pre-surgery patients (deemed to be safe) and additional studies on ink used in tattoos. Tattoo ink is not regulated by the Food and Drug Administration (FDA) and may contain metal salts.
Source:http://chemistry.about.com/library/weekly/aa121602a.htm
