Capzasin is currently made by Sanofi US, headquartered in New Jersey. They also make many other topical products (including Icy Hot and Aspercreme), vaccines, and prescription medications.
CAPZASIN-HP ACTIVE INGREDIENTS
Capzasin-HP has just one active ingredient:
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.
CAPZASIN-HP SIDE EFFECTS
There are no known major side effects for using Capzasin topically (on the skin, external use only) as directed. Although one should seek medical attention if severe allergic reaction occurs. Not a good idea to use on broken or damaged skin, and be sure to keep it clear of the eyes - ouch.
If you are pregnant or breast feeding, ask your doctor before use.
I found an established body of research that may suggest the use of capsaicin 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.
You can purchase Capzasin-HP at most major pharmacies. You can also find it on Amazon.