To expand on my subject line, I’m speaking of products like IcyHot, Bengay, Salonpas, etc. These are all products that use either menthol or capsacin to produce a hot or cold sensation, and claim to relieve pain.
I find myself wondering if any of these products actually have a beneficial effect. My questioning started after I bought two different pain-relieving products at the same time: an Aspercreme “heat therapy” cream and an IcyHot “Cold Therapy” gel. I looked at both products’ ingredients, and both products listed menthol as the “active ingredient”. Ooookaaay. So it’s menthol providing both the “hot” and “cold” effects.
So the question is, do these topical treatments actually do anything beyond generating a hot or cold sensation in the skin? Obviously, some products, like wraps that use some sort of physical, chemical reaction (apparently using iron filings) to generate actual, measurable heat, or actual icepacks to produce “cold” probably have some beneficial effect. But it seems to me that topical treatments using menthol or capsacin to generate the sensation of hot or cold can’t possibly have any real effect, beyond possibly helping with relaxation.
I use Salonpas on occasion. At the very least, it does a good job of distracting me from the pain
In my thoroughly non-medical opinion, I suspect that anything that allows you to keep the area relaxed will help the healing process, if just a little.
I tried putting this stuff (menthol and camphor in a petroleum jelly) on one forearm and comparing the infrared radiation from each arm with a contactless thermometer. No observable difference, but my method was pretty crude. Something to do next time you are bored and sick in bed.
Wikipedia says that tmenthol and capsaicin do not cause temperature change, but that menthol and camphor can both cause vasodilation, which I would have thought might change skin temperature, from what I’ve learned about hypothermia. Capsaicin can also cause inflammation, which I’d think might warm the skin. Any comments from someone who actually understands these processes?
Sensations can inhibit other sensations, so you might block perception of something unpleasant with the odd feelings that these ointments cause. I think this topical pain relief is the medicinal effect they are approved for.
Anecdotal secondhand advice: incident radiant heat enchances the effect (perhaps by speeding the reaction of the menthol with the cold receptors in your skin?), which can be uncomfortable. The effect fades only slowly after removal of the external heat. Avoid, especially on large areas of skin.
There are endless papers on the effects of menthol; I just did a quick search through the Cochrane Library (no, they don’t have a systematic review). Is there anyone who is actually an expert in this subject on the boards? Failing that, you could write to the authors of one of these papers.
Summary from the above link:
Rubefacients cause irritation and reddening of the skin, due to increased blood flow. They are believed to relieve pain in various musculoskeletal conditions, and are available on prescription and in over-the-counter remedies. This review found evidence that was limited by the quality, validity and size of the available studies, particularly for studies in acute pain conditions like strains and sprains, where there was inadequate information to support the use of rubefacients. In chronic pain conditions such as osteoarthritis the evidence was more robust, but rubefacients appear to provide useful levels of pain relief in one in six individuals over and above those who also responded to placebo. This compares poorly with topical NSAIDs where substantial amounts of good quality evidence indicate that one in every three individuals treated will experience useful levels of pain relief over and above those who also responded to placebo.
Menthol and capsaicin are rubefacients, though I don’t think capsaicin was necessary tested for here. There is evidence capsaicin works via its effect on pain nerve fibers.
Taken to an extreme, horses with lameness used to be “blistered” or “fired”. A caustic liniment was applied, burning the area over an injury. The horse often did better on the leg, likely due to resting the animal for the time it took for the burns to heal.
ISTR, I read an article that stated the only benefit from those creams was the massage you gave yourself, or were given by someone else while applying said cream.
Sorry I don’t have a cite.
I’ve used capsaicin for unrelenting Trigeminal Neuralgia pain. It doesn’t always work but when it does, it’s a fucking miracle cure. It makes the pain far, far worse for a brief but intense time and then…quiet. It’s like it resets my nerves when nothing else can.
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