Dr. Charles Shubin, director of pediatrics at Mercy FamilyCare in Baltimore, Md., says that there are approximately 150 diseases that are considered "common," and countless others that are uncommon. It's enough to make a parent's head spin. So should parents educate themselves on every possible disease out there?

No, says Dr. Karin Sadow, medical director at PM Pediatrics in Mamaroneck, N.Y. "Doing so will ultimately give the caretaker something to worry about," she says. "There are many uncommon illnesses, and it would be difficult and probably unhelpful to know a little bit of information about many uncommon diseases."

Instead, she says, if your child exhibits behavior or symptoms that seem alarming or out of sorts, don't hesitate to call the doctor for advice or a visit.