ABOUT SALONPAS
Salonpas are the first and only (to-date) FDA-approved over-the-counter pain relief patch. Their website notes that all other pain patches on the market are indicated for only minor pain with relief up to eight hours and Salonpas are labeled effective for mild to moderate aches and pains with relief up to twelve hours. Well, alright smarty-patch.
Salonpas are manufactured by Hisamitsu Pharmaceutical Co., Inc. of Tosu City, Japan. The company produces a variety of prescription and over-the-counter transdermal patches and skin care products.
According to their website, the product name comes from its active ingredient methyl salicylate. They took the sal in salicylate and because that compound passes through the skin, they added the pas, and landed on SALONPAS. Salicylate + pas = salonpas. Hrm... but what about the o? These are the things that keep me up at night.
There are several variations of the product beyond their standard Pain Relief Patch. There's also Arthritis Pain, Versatile, Hot, Air, Gel, Aqua-Patch, and Gel-Patch.
SALONPAS ACTIVE INGREDIENTS
METHYL SALICYLATE
Also called wintergreen oil, this organic ester is naturally produced by many species of plants, particularly wintergreens. It can also be synthetically produced.
Wintergreen oil (along with menthol, eucalyptus oil, camphor, and turpentine oil) is known as a counterirritant. Counterirritants create a feeling of cold or heat that may overpower the localized sensory information from a sore joint or muscle.
Wintergreen oil is a salicylate. Salicylates are compounds related to aspirin. By using them topically, it may help someone avoid most of the negative side effects of taking aspirin or aspirin-related compounds by mouth, such as:
ulcers of the stomach and small intestine,
abdominal pain,
nausea,
gastritis (inflammation of the stomach)
A randomized, double-blind, parallel-group, placebo-controlled, multicenter study published in 2010 concluded, "A single, 8-hour application of a patch containing methyl salicylate and l-menthol provided significant relief of pain associated with mild to moderate muscle strain in these adult patients compared with patients receiving a placebo patch."
Additionally, a study of collagen-induced arthritis in mice published in 2014 concluded, "[methyl salicylate] has great potential to be developed into a novel therapeutic agent for the treatment of RA."
However, in its pure form, methyl salicylate is toxic, especially when taken internally.
People should never exceed the directions on the label due to the risk of salicylate toxicity (aspirin poisoning). A single teaspoon (5ml) of methyl salicylate contains 7g of salicylate, which is equivalent to more than twenty-three 300 mg aspirin tablets. It has proven fatal to small children in doses as small as 4ml. Every rose has its thorn, right?
To lighten things up... literally... when you mix methyl salicylate with sugar and dry it, methyl salicylate is triboluminescent. Which is almost as fun to say, as it is to see.
It's an optical phenomenon in which light is generated through the breaking of chemical bonds in a material when they are pulled apart, ripped, scratched, crushed, or rubbed. So next time you've got some Wintergreen Life Savers and a dark room, try it out.
MENTHOL
This is an organic compound made synthetically or obtained from mint oils.
Menthol stimulates the transient receptor potential channel melastatin 8 (TRPM8). This receptor is responsible for the well-known cooling sensation it provokes when inhaled, eaten, or applied to the skin.
It also has weak analgesic (pain-killing) effects due to its selective activation of our κ-opioid receptor. This protein mediates many effects including changing our perception of pain, consciousness, motor control, and mood.
CAMPHOR
This waxy solid has a strong aromatic odor and is found in the wood of the evergreen tree Cinnamomum camphora; Dryobalanops aromatica; Ocotea usambarensis; and dried rosemary leaves (Rosmarinus officinalis). It is easily absorbed through skin and produces a cool-feeling like menthol.
CAPSAICIN
Present in the Hot (0.025%) and Gel-Patch (0.025%) products.
Capsaicin is an active component of plants belonging to the genus Capsicum (chili peppers). It stimulates the transient receptor potential cation channel subfamily V member 1 (TrpV1) which may provide a sensation of heat.
A study published in 2011 summarized that topical capsaicin reduces skin hypersensitivity and pain by a process described as "defunctionalization" of nociceptor fibers. A nociceptor is a nerve cell gives a shout out to the spinal cord and brain when it senses potentially damaging stimuli and usually causes the perception of pain. This "defunctionalization" process is rather complex, so I'd suggest reading the study to learn more.
Additionally the study stated that a meta-analyses of numerous studies on low-concentration capsaicin formulas (like SALONPAS) produced safe and modest efficacy. However, a high-concentration (8%) capsaicin formula, specifically a patch called Qutenza™, produced effective pain relief for up to 12 weeks. Hrm, I might be trying that on for size.
SALONPAS SIDE EFFECTS
There are no known major side effects for using Salonpas as advised (on the skin, external use only), although one should seek medical attention if a severe allergic reaction occurs. It's also not a good idea to use on broken or damaged skin, and be sure keep it clear of the eyes - ouch.
PRECAUTIONS AND WARNINGS:
Methyl Salicylate (wintergreen oil) might cause an allergic reaction in people who are allergic to aspirin or other salicylate compounds, or have asthma or nasal polyps. Use wintergreen with caution if you have one of those conditions.
Wintergreen oil can be poisonous for children. Taking 4-10 mL of wintergreen oil by mouth can be deadly. So keep away from the kiddos and do not use wintergreen oil on the skin of children less than 2 years old.
If you are pregnant or breast-feeding, wintergreen is safe in amounts found in food, but there's inconclusive evidence to know if it's safe in the larger amounts internally or topically. Either clear usage by your doctor, or select a topical gel that does not include wintergreen oil (methyl salicylate) on the ingreidents label.
SALONPAS SUMMARY
I found an established body of research that may suggest the use of menthol and wintergreen oil for mild pain relief. Given the very low risk and very limited side effects, it would seem worth a try for individuals seeking a complementary and/or off-the-shelf product for pain relief.
They're quickly becoming commonplace right alongside staples like Icy Hot and Bengay at pharmacies and big box stores like Walmart. Or, you can purchase the small patches, large patches, or gel on Amazon.
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