Ringing in the ear, or tinnitus, can occur in either or both ears. According to the American Tinnitus Association, more than 50 million people in the United States have had some degree of tinnitus. Two million of these are disabled by tinnitus.
The loss of cilia, tiny hair cells in the inner ear, is one reason tinnitus occurs. The process of aging, exposure to loud noise or ear trauma can damage cilia.
Tinnitus often accompanies hearing loss. It does not cause hearing loss, but a hearing impairment may make tinnitus more noticeable.
Some medicines can damage the ear, and some can produce tinnitus as a side effect. These medicines are known as ototoxic drugs and include nonsteroidal anti-inflammatory drugs, some antibiotics and diuretics, and certain drugs for the treatment of cancer.
A buildup of wax or fluid in the inner ear impairs the cilia's ability to transmit information about sound to the brain. The brain then misinterprets the information, resulting in tinnitus.
There are medical conditions that either produce tinnitus or interfere with the brain's ability to interpret sounds. These conditions include stress, infections, sinus problems, high blood pressure, misalignment of the jaw, Lyme disease, Meniere's disease and brain tumors.