Chili peppers have traditionally been used as a topical painkiller, with capsaicin creams available in tubes or jars or as the active ingredient in heating pads for sale at most drugstores. It can also relieve itching (pruritis). Among the conditions it is used for are back pain, bursitis, fibromyalgia, joint pain, muscle pain, nerve pain, osteoarthritis, pain due to diabetic, neuropathy, phantom pain after amputation, post-herpetic neuralgia, post-surgical neuropathic pain, and rheumatoid arthritis.
Capsaicin or 8-methyl N-vanillyl 6nonamide is one of the six capsaicinoid compounds in chili peppers, and is what gives them their distinctive mouth-burning, eye-watering, and sweat-breaking spiciness. It
works by activating the chemical terminals of sensory neurons which increases membrane permeability to elements like calcium and sodium, thereby triggering the release of substance P, the substance responsible for the sensations of pain we experience inside our mouths when eating a habanero chili pepper. The chemical terminals are receptors called transient receptor potential cation channel subfamily V member 1 (TRPV1). When they bind with capsaicin, they open and allow the latter to enter specific pain fibers, letting extra calcium inside the cells until the nerves become overloaded and shut down. When these cells shut down, it temporarily numbs the feeling in that specific area where it was applied.
The brain responds to the burning sensation by releasing endorphins, the body's natural painkiller.
Endorphins are a class of neurotransmitters produced by the body to respond to any kind of pain, and bonds to some of the same receptors in the brain as the opioid morphine. The term itself is a blend of two words coined by American scientists Rabi Simantov and Solomon H. Snyder, “endogenous” and “morphine" and literally means "morphine produced naturally in the body.” Endorphins are also known to cause a sense of well-being, and is the attributed cause of a phenomenon called “runner's high.” This is largely because its release is triggered by exercise, which puts a great deal of wear and tear on the body and causing muscle pain. The muscle pain in turn becomes the signal for the body to release endorphins. Similarly, capsaicin has also been known to trigger the release of endorphins.
But it is the feeling of numbness that scientists would like to explore further. By bathing surgically exposed nerves in a high enough dose of capsaicin, the area should be numbed for weeks, translating to less pain and suffering for those who have just undergone surgery. It means that patients will require fewer opioid painkillers as they heal. Opioid painkillers are also fraught with serious side effects that limit their use, and are potentially addictive. The most common side effects of opioids (morphine) include euphoria, drowsiness, nausea, vomiting, constipation, dilated pupils and respiratory depression. Some side effects may be harmful or even lethal. But with capsaicin, research suggests that a one-time dose applied to the wound that works inside the wound, allowing patients to start physical therapy after surgery without needing to be incapacitated by the side effects of opiate-based painkillers.
Although the application for chili peppers for pain relief after surgery is yet to be approved by the US Food and Drug Administration, many scientists are optimistic that capsaicin is the future of pain relief.
