An exothermic natural massage shell includes a natural bivalve shell comprising a first half and a second half adhered together with an adhesive to form a hollow chamber. An aperture is formed in the first half to provide a portal to the hollow chamber of the bivalve shell. A reactant is disposed inside the hollow chamber of the bivalve shell. The reactant may be a reactive powder mixture disposed inside a fluid-permeable pouch. Combining the reactant with an activator inside the hollow chamber of the bivalve shell causes an exothermic reaction that heats the bivalve shell and maintains the bivalve shell at a substantially constant elevated temperature for a duration of time. The adhesive adhering the first shell half to the second shell half includes a first elastomeric polymer bonding agent with balanced coefficient of expansion properties and a second flexible resin sealant that makes the adhesive moisture-proof.