Physical Danger
Sure, you might be exposed to some gross bodily functions, including projectile vomit, urination, defecation, and more forms of secretions than you probably ever knew existed. You might find yourself chasing kids through malls, or deflecting the bites of angry, teething toddlers. You might spend your waking minutes freaking out about the kids' physical safety, but you won't need to worry about your own too much.
So unless your young charge turns out to be like that creepy kid in The Sixth Sense, you're probably okay. Which reminds us…if the kid you're taking care of suddenly spins her entire head around on her neck or says something like "You have seven days," get out of there pronto. Save yourself.