Eustachian tube dysfunction occurs when the tube connecting the middle ear to the back of the throat becomes blocked or fails to open properly. This can lead to a feeling of fullness in the ear, discomfort, and difficulty hearing. It often results from allergies, colds, or sinus infections that cause inflammation and swelling. When the Eustachian tube does not function correctly, it can disrupt the balance of air pressure in the middle ear. This imbalance may cause pain and can lead to complications like ear infections or fluid buildup. Treatment options include decongestants, nasal sprays, or in some cases, surgical intervention.