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Why does swallowing help equalize pressure in the middle ears?

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Illustration showing different animals and their respiratory organs: a spider with book lungs, a chicken with lungs, a sponge with labeled inflow and outflow pores, a fish with gills, and a caterpillar with spiracles. — Respiratory system Different methods of respiration in animals.

Swallowing helps equalize pressure in the middle ears because it triggers the opening of the eustachian tube.12

The eustachian tube is a hollow structure that connects the middle ear to the nasopharynx, the space behind the nasal passages. Under normal conditions, this tube remains closed at rest to protect the middle ear. However, when you swallow, the tube opens, allowing air to pass between the nasopharynx and the middle ear cavity. This process ventilates the middle ear and ensures that the air pressure on both sides of the tympanic membrane (eardrum) remains equalized.1324

Without this mechanism, significant pressure differences—such as those experienced during rapid altitude changes or underwater diving—can cause the eardrum to bulge, leading to pain, inflammation, or even rupture. Swallowing provides a simple, often unconscious way to adjust these minor pressure differences.412