Sudden congestion in the left ear is mostly considered to be caused by secretory otitis media, which is mostly caused by upper respiratory tract infections. When upper respiratory tract infection occurs, it can cause congestion and swelling of the mucosa of the nasal cavity and nasopharynx, resulting in congestion and swelling of the mucosa of the eustachian tube, which prevents air from entering the tympanic cavity through the eustachian tube, causing negative pressure inside the tympanic cavity, thus causing congestion in the ear. Treatment requires controlling the infection and improving the function of the eustachian tube. Oral antibiotics such as cefprozil can be taken, and if necessary, hormones such as prednisone and mucus promoters such as Cernod can be added to reduce edema, and nasal drops of 1% furosemide can reduce the congestion and swelling of the eustachian tube and improve the function of the eustachian tube, thus eliminating the congestion of the ear.