There are many causes of ear pain on one side, commonly due to otitis media, otitis externa, boils on the external ear canal, and cholesteatoma of the external ear canal. 1.. Otitis media: the disease is related to pathogen infection and Eustachian tube dysfunction. When one ear suffers from otitis media, it can manifest as ear pain, discharge of secretions from the ear canal, hearing loss, tinnitus and other symptoms. 2. Acute otitis externa: acute otitis externa can cause patients to appear on one side of the ear pain phenomenon, usually otitis externa and the outer ear canal skin resistance decline, pathogen infection, etc. Related to the acute inflammation of the skin of the outer ear canal or subcutaneous tissue. The acute inflammation of the skin or subcutaneous tissues of the external auditory canal is characterized by swelling and pain in the ear, which is gradually aggravated by sitting or lying down, and aggravated by chewing or talking. 3. External auditory canal boil: limited purulent inflammation of the skin of the external auditory canal, due to the small amount of subcutaneous tissue of the external auditory canal, the skin and cartilage membrane are tightly adhered to, and the inflammation stimulates the nerve endings, which can be manifested as severe pain in one ear. 4. Cholesteatoma of external auditory canal: the etiology is not clear, but it can cause one side of ear pain in some patients. In the early stage of the disease, some patients may be asymptomatic or have mild symptoms. With the progress of the disease, patients will experience discomfort such as occlusive sensation in the ear, tinnitus, headache and hearing loss. Auricular cartilage inflammation, tuberculosis of the outer ear, ear trauma, etc. can also cause pain in one ear, and it is recommended that the patient consult a doctor in time for a clear diagnosis and treatment.