A chemical that may help relieve chronic pain. Capsaicin is found in capsicum peppers, which include cayenne peppers, red peppers, African chilies, and tabasco peppers. It is capsaicin that gives these chili peppers their bite.
Capsaicin appears to relieve pain by stimulating the release of substance P, a chemical transmitter of pain, from nerve terminals. Initially, the release of substance P causes pain (or an exciting kick in the tastebuds), but eventually the nerve terminals become depleted of substance P, leading to loss of the pain sensation (and numb lips in lovers of Thai and Indian food). This painlessness generally lasts as long as capsaicin is present and depleting substance P from the nerves. Substance P is not the sole transmitter of pain, however, so capsaicin may only be effective in certain types of pain.
In the form of cayenne peppers, capsaicin has been used with variable success in folk medicine since the 1800’s for such diverse conditions as colds, allergies, arthritis, and hemorrhoids. It is available in the form of over-the-counter topical salves, sold under the brand names ArthriCare and Zostrix, among others, which have been approved by the Food and Drug Administration for treating chronic pain. Although there have not been large, controlled clinical trials proving the effectiveness of these salves, they at least appear useful in relieving pain from shingles, trigeminal neuralgia (a nerve disorder that causes facial pain), arthritis, and painful diabetic neuropathy (nerve damage).
Capsaicin’s success in relieving pain from diabetic neuropathy is highly variable: Sometimes it helps, sometimes it doesn’t, and occasionally it actually makes the pain worse. If you have painful diabetic neuropathy, one of these salves may help relieve the pain, but it is a good idea to consult your doctor before trying it.