"I don't see any basis for it, as far as equalizing the pressure," said Dr. George B. Stoneman, an ear-nose-throat specialist at Good Samaritan Hospital, Los Angeles, and associate clinical professor of otolaryngology at USC. "And the moisture would be detrimental."

Definitely, said Stoneman, who warned that travelers with acute sinus or ear infections should not try it. Nor should those who have had recent ear surgery. For others, the maneuver helps equalize the pressure on both sides of the eardrum. "The only time you need to do it is when you are descending," he said. As a plane descends, pressure on the outside of the eardrum increases and pressure behind the drum does not. On ascent, the equalization of pressure behind and in front of the eardrum usually happens naturally, he added.

"I doubt if 7-Up helps," said Dr. Robert Marks, a University of Alabama assistant professor of medicine. A better bet, he said, is chewing gum. In a recent study, Marks and co-researcher Dr. Swarnjit Singh found that chewing gum after a meal reduced the amount of time acid stays in the esophagus, thus relieving heartburn in 7 of 10 subjects.