A disposable plug has a mask with an orifice aligned at the entry into the ear canal when the plug is inserted into the ear. A sealed envelope has a leading elastic tip that extends forward of the orifice into the ear canal and a trailing reservoir that extends rearward of the orifice. A super-cooled liquid salt substantially fills the envelope. The envelope is sized to contain a sufficient quantity of the liquid salt to deliver heat to the inner ear at a predetermined temperature for a predetermined time period. A convex disk in the reservoir can be manually popped to concave after the tip of the envelope has been inserted into the ear canal to shrink the reservoir and expand the tip into deeper extension into and compliance with the ear canal and to activate solidification of the liquid salt to generate heat into the ear canal.