Mar. 23 -- FRIDAY, Feb. 1 (HealthDay News) - An over-the-counter ear wax softener may cause inflammation and damage to the eardrum and inner ear, and harm hearing in the process, report Canadian researchers who made the discovery in an animal study.
The researchers looked at the effect of a softener called Cerumenex on hearing and the ear cells in chinchillas, a standard model for this type of research.
The product is no longer sold in the United States, according to a spokesman for its manufacturer, Purdue Pharma LP.
"Purdue discontinued U.S. distribution of this product in 2002," James Heins said. But, he added, the product is still marketed in Canada and Europe.
In the study, published recently in The Laryngoscope, a team led by Dr. Sam Daniel, director of the McGill University Auditory Sciences Lab at The Montreal Children's Hospital, inserted tympanostomy tubes in one of the ears of five chinchillas.
These tubes are often used in children with middle ear infections, to keep fluid from accumulating behind the ear drum. The chinchilla has a hearing mechanism similar to humans, Daniel explained in a prepared statement.
His team assessed hearing in both ears of all the animals and then introduced the wax softener, which is dropped into the ear canal, into the ears with the tubes.
In four of five ears with tubes, the researchers noticed swelling, crusting and fluid accumulation. One animal developed facial paralysis on the side treated with the softener.
The ears without the tubes served as the controls. When the team evaluated the animals' hearing, they found a reduction in hearing in the treated ears, as well as damage to the treated ears' nerve cells. Some of the effects occurred after just one of the four doses had been given.
Daniel and his colleague recommended caution in using the wax softener if the status of a person's eardrum is not known.
Randy Steffan, a spokesman for Purdue Pharma in Canada, said that the company is aware of the study and plans to follow up with the Montreal Children's Hospital researchers to review the full results.
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