Parents are often quick to get out their thermometer whenever their baby feels warm or seems sick, with a runny nose, cough, or some extra fussiness.

And that used to mean using a mercury thermometer, which were long thought to be the best for taking a child's temperature.

That was before experts spread the word about the dangers of mercury, even the small amount in a mercury thermometer. Now, the American Academy of Pediatrics recommends that parents avoid using mercury thermometers.