Why do nasal allergies effect the ear? how do they muffle sound and cause pressure?

Eustachian tube dysf: Inflammation of the nasal pharyngeal area due to environmental allergies can stuff up the eustachian tube, which is the connection tube between your inner ear and the outside world. When the inner ear cannot communicate with the outside air, there would be a difference in pressure between the 2 areas causing your ear to pop and have pressure.