You think you may have a fever. But you only have one of those in-the-ear toddler thermometers. Will it work on an adult? Loyola University Medical Center says YES. In fact, many hospitals use ear thermometers on adults because they’re faster, more accurate and more comfortable than under-the-tongue models. They use an infrared beam to measure the temperature of blood vessels under the eardrum, where skin is thinnest. But since you can’t see inside your own ear, keep this in mind: For an accurate self-test, pull your ear up and back, and angle the tip of the thermometer in your ear, toward your nose. Because the eardrum is slightly forward in the ear canal.