Concept

• Rapid changes in air pressure cause unequal pressure between the middle ear and the outer ear. The Eustachian tube, which connects the middle ear to the nasal passages, might not expand in time to respond the the pressure change, leading to pain and a "popping" sensation. Chewing gum encourages that expansion.
  
  

Process

• The swallowing action that accompanies gum chewing stimulates the Eustachian tubes' muscles, opening the tubes and allowing air to move freely to and from the middle ear. The air pressure inside the ears then equalizes with the outside air pressure, relieving discomfort.
  
  

Considerations

• Airplane passengers without access to chewing gum can also yawn, take a drink or suck on candies to restore the pressure balance inside the Eustachian tubes. People with severe sinus congestion should avoid flying altogether. Their ears might not respond to attempts to equalize the pressure buildup, which could then result in eardrum damage during the flight.