From the manufacturer:
Child safe inks are ideal for younger stampers as they are water-based, kid safe and non-toxic. Just For Kids ink pads are specially formulated with non-toxic ingredients approved by the FDA for use by children. They are a quick drying, non-solvent, water based ink. Contains FD&C approved ingredients and conforms to ASTM-D4236. This package contains one 3.75x2.25 inch inkpad. Available in assorted colors, each sold separately. Made in the USA.