The bottom line
It’s generally better to target pain locally, if possible, since some oral treatments can impact the gut or have unwanted systemic effects. Hence, the widely available Salonpas patches can be helpful.
One of the types of Salonpas patches is even FDA approved, which is rare or even unprecedented for an over-the-counter pain patch. That doesn’t mean it’s more effective than other patches (especially with similar ingredients), but it has been studied in a randomized trial.
How do Salonpas patches work?
You don’t have to look any further than the name! The SAL stands for Salicylate, and the PAS means Pass (believe it or not, this is true). So the patch PASses methyl SALicylate through your skin, over to the tissue that is hurting.
Now, this isn’t readily apparent by looking at the name. It’s not like pain sufferers are hunting for Salicylate-containing products on the shelf. Salonpas, to me, just sounds like a vaguely foreign name for a ubiquitous patch (French-sounding even though it’s Japanese).
Anywho, back to the active ingredients. Methyl salicylate is produced by certain plants as a toxic compound to kill predators (typically, insects). When used for pain, it works by acting as a counterirritant – basically, causing mild irritation to the tissue and distracting from the pain stimulus.
Salonpas typically has 10% methyl salicylate, but it can range from zero up to 15%. Different Salonpas patches can include other counterirritants as well, such as menthol and camphor, and even capsicum (the capsaicin extract from peppers is uniquely effective due to acting on a type of receptor named TRPV1, but it can also burn like hell).
Not many pain patches have been investigated in clinical trials, but Salonpas has been tested in people with muscle strains, in a randomized controlled trial, and found to be effective.
Do Salonpas patches have any side effects?
You might think they’re innocuous, since they’re so widely available and not taken orally. You would be wrong!
A seventeen year old runner in New York died in 2007, after using excessive amounts of topical muscle-pain products containing counterirritants. An 80 year old man in California had methyl salicylate oil regularly rubbed on his legs by a caregiver, and then mistakenly drank it and died.
This doesn’t mean you’ll die from using pain patches though. Keep use to minimal-to-moderate levels. And if you have a local reaction, like inflamed skin, stop.