Theoretically, antihistamines may reduce the congestion of mucous membranes and decrease obstruction of tubes lined by mucous membrane, such as the Eustachian tube. An open Eustachian tube would allow the middle ear pressure to equalize to ambient air pressure. It may also allow drainage of fluid from the middle ear.

Antihistamines can be effective in relieving clogged ears, but only if the underlying cause is related to allergies. When you have an allergic reaction, your body releases histamines that cause the mucous membranes in the Eustachian tubes (the passages connecting your middle ear to your throat) to swell and produce fluid. This inflammation prevents the tubes from equalizing pressure, leading to that muffled, "clogged" sensation. By blocking the histamine response, these medications reduce swelling and allow the ear to drain and ventilate properly. However, if your ears are clogged due to a common cold, a sinus infection, or sudden changes in altitude (like on a plane), a standard antihistamine may not be the best choice; in those cases, a decongestant or a nasal steroid spray is often more effective. In 2026, doctors frequently recommend second-generation antihistamines (like cetirizine or loratadine) because they are non-drowsy. If the "clogged" feeling is accompanied by pain, fever, or hearing loss, it is essential to see a professional to rule out a middle ear infection.