Pure shellac is 100% non toxic - it's made from excretions of the lac bug - the prepacked shellac is not pure it has additives to improve shelf life and will require a gas off period if you can locate shellac flakes and dissolve them in denatured alcohol this is the best. the alcohol will evaporate completly in only a few hours. I personally prefer waterborne acrylics though - these are more resiliant to scrating and use - whereas shellac wears off fairly quickly and has to be refreshed from time to time.