Hedgehogs have long spines, or quills, made of keratin. They do not come off easily, unlike porcupines, but in baby hedgehogs, the baby quills drop off and are replaced with adult quills. This is called "quilling". When they are very stressed or sick, their quills can fall off, too. Their quills are not poisonous: they are safe for humans to feel and touch, as they are not very sharp, or harmful.