List of products in the National Drug Code with proprietary name . Acetic acid is used to treat an outer ear infection (external otitis). It works by stopping the growth of bacteria and fungus. Treating the infection reduces pain and swelling in the ear. Wetness in the ear canal can help bacteria and fungus to grow. This medication may also contain drying ingredients such as glycerin or alcohol. Drying of the ear canal helps to cure the infection.