The Eustachian tube is a narrow passage that connects the middle ear to the back of the throat. Its primary function is to equalize air pressure on both sides of the eardrum, which is essential for proper hearing. When you swallow or yawn, the tube opens briefly, allowing air to flow in and out. This tube also helps drain fluid from the middle ear, reducing the risk of infections. If the Eustachian tube becomes blocked due to allergies, colds, or sinus infections, it can lead to discomfort, hearing problems, or conditions like otitis media.