"Historically, pain management for children in general was very limited. But the world has changed. Now clinicians are solidly on board trying to manage pain," says Fran Porter Lang, a Washington University psychologist and authority on pediatric pain.

"They can't tell us that it's pain, but their responses are indicative of pain," Lang says. "We're really understanding that babies can feel as much pain, if not more, than older children and adults."

Research on sugar as a pain-reliever began with premature infants in intensive care units. Although preemies undergo many painful procedures, they are not good candidates for frequent doses of pain medications. Doctors found that sugar, often given with a pacifier, was an effective and benign alternative.