Capsaicin is an active component of chili peppers and proven through clinical trials as an effective treatment of muscular aches. When applied externally, such as in a pain patch, capsaicin activates specific nerve receptors causing local heat, stinging and/or itching sensations. Prolonged activation of these receptors causes them to lose their ability to function properly (and process pain signals) for extended periods of time.
Many studies have shown that capsaicin effectively reduces pain from osteoarthritis, rheumatoid arthritis and fibromyalgia. In a 2010 German study, joint pain decreased nearly 50 percent after three weeks' use of 0.05 percent capsaicin cream. (Arthritis Foundation)
According to a study by the European Neurology Review (2012)
“Capsaicin has long been used as a traditional medicinal extract to treat pain and, recently, its mechanism of analgesic action has been discovered. In three recent randomized controlled trials, a patch containing capsaicin demonstrated meaningful efficacy and tolerability relative to a low-concentration capsaicin control patch in patients with peripheral neuropathic pain.”