To Your Health
January, 2007 (Vol. 01, Issue 01)
While the capsaicin receptor TRPV1 has been known for several years, only recently did researchers discover the specific receptor for menthol. This newly discovered receptor is called TRPM8.
These receptors are being investigated for their role in chronic pain control. Some investigators believe these receptors are a key link because of the close link between temperature and pain in the central nervous system.
TRP receptors are activated at specific ranges of temperatures on the skin, or by specific chemicals such as menthol. When activated, these receptors stimulate sensory fibers, changing thermal stimuli to chemical signals. These signals travel to the central nervous system in the spinal cord, where the stimulus is perceived as hot or cold.
Topical analgesics provide temporary pain relief. The amount of relief depends on several factors: the active ingredient, the amount of the ingredient and the length of treatment. The amount of relief also depends on the cause of the pain. For example, research has shown that capsaicin is effective for arthritis (both osteoarthritis and rheumatoid arthritis), as well as diabetic neuropathy.
Menthol has been shown to be effective for managing hand arthritis, neuropathic pain, sports injuries and headaches. Unfortunately, much more research is needed to determine the effectiveness of these ingredients on many other conditions. With the recent discovery of the TRPM8 receptors and their influence on chronic pain, we can learn more about the effectiveness of substances such as menthol in the treatment of both acute and chronic pain.
Topical analgesics simply are pain-relieving creams or gels that are applied to the skin at the point of pain. This helps concentrate the pain relief at the point of the problem, without having to wait for medication to be absorbed internally before taking effect. In contrast to oral medications, natural pain relief can be provided without possible side effects such as ulcers, liver or kidney damage. While topical analgesics are fast-acting, they occasionally do need to be re-applied.
For example, The American College of Rheumatology recommends topical analgesics such as capsaicin and menthol for patients with knee arthritis as a "front-line" treatment before expensive and potentially harmful prescription anti-inflammatories. They recommend applying these topical analgesics up to four times a day for temporary pain relief.
Menthol also can be applied for "cryotherapy" or cold-therapy without the side effects of cold packs or ice. Researchers have shown that menthol provides similar effects of ice, such as increased pain threshold and increased cutaneous circulation. Using menthol, these effects can be produced without decreasing skin temperature, stiffness, decreased elasticity, skin irritation or prolonged vasoconstriction ... all disadvantages to using cold packs and ice treatments. This can be particularly advantageous when providing cryotherapy to athletes, for example.