Answer: Compounds in Tiger balm activate the transient receptor potential cation channel M8 (TRPM8).
Tiger balm is a topical waxy ointment that is rubbed directly onto the skin. Within 15 minutes, it produces a mixed cool and warm sensation. It is used to alleviate muscle pain and soreness.
The compounds in Tiger balm are absorbed transdermally. Once permeating the skin, they can act on the transient receptor potential cation channel M8 (TRPM8) proteins, which are expressed on nociceptors. Activation of TRPM8 causes depolarization through the entry of Na+ and Ca2+ ions. This depolarization causes action potentials to be sent towards the central nervous system by the anterolateral system, carried via the A delta and C fibers. Activation of these receptors produces a cooling sensation. This cooling sensation overwhelms the competing painful stimuli that the sore muscles are also sending.
Tiger balm contains menthol and camphor. Menthol is an agonist for the TRPM8 receptors. Camphor can activate TRPM8 receptors as well as the vanilloid receptors TRPV1 and TRPV3, which produce the sensation of heat.
Tiger balm is available for purchase over-the-counter.