The capsicum family includes red peppers, bell peppers, pimento, and paprika, but the most famous medicinal member of this family is the common cayenne pepper.
Cayenne and related peppers have a long history of use as digestive aids in many parts of the world, but the herb's recent popularity has, surprisingly, come through conventional medicine.
Many people think that hot peppers cause inflammation to tissues, and that this is the source of the classic hot pepper sensation. However, hot peppers don’t actually have any damaging effect; they merely simulate the sensations produced by damage. (Herbs like garlic, ginger, horseradish, and mustard actually can cause tissue damage.)
Here’s how it works: All hot peppers contain a substance called capsaicin. When applied to tissues, capsaicin causes release of a chemical called substance P. Substance P is ordinarily released when tissues are damaged; it is part of the system the body uses to detect injury. When hot peppers artificially release substance P, they trick the nervous system into thinking that an injury has occurred. The result: a sensation of burning pain.
When capsaicin is applied regularly to a part of the body, substance P becomes depleted in that location. This is why individuals who consume a lot of hot peppers gradually build up a tolerance.
It’s also the basis for a number of medical uses of capsaicin. When levels of substance P are reduced in an area, all pain in that area is somewhat reduced. Because of this effect, capsaicin cream is widely used for the treatment of various painful conditions.
Under the brand name Zostrix, a cream containing concentrated capsaicin has been approved by the FDA for the treatment of post-herpetic neuralgia, the pain that often lingers after an attack of shingles. There is also relatively good evidence that topical capsaicin can modestly decrease the pain of diabetic peripheral neuropathy, other forms of peripheral neuropathy nerve pain following cancer surgery, as well as the pain of arthritis. Capsaicin cream may also be helpful for other forms of pain, including fibromyalgia, back pain, and cluster headaches.1,2,3,4 However, the benefits seen with capsaicin are seldom dramatic; in many cases, other pain relieving treatments are used simultaneously.
Besides pain-related conditions, some evidence indicates that topical capsaicin may be helpful for psoriasis and possibly other skin conditions as well (especially those that involve itching).
Cayenne can be taken internally as well. It appears that oral use of cayenne might reduce the pain of minor indigestion ( dyspepsia). This may seem like an odd use of the herb; intuitively, it seems that hot peppers should be hard on the stomach. However, remember that hot peppers don’t actually damage tissues—they merely produce sensations similar to those caused by actual damage. Apparently, by depleting substance P in the stomach, they reduce sensations of discomfort. In fact, some evidence suggests that oral use of cayenne or capsaicin can actually protect the stomach against ulcers caused by anti-inflammatory drugs .5,6,7 However, contrary to some reports, cayenne does not appear to be able to kill Helicobacter pylori, the stomach bacteria implicated as a major cause of ulcers.9
In a double-blind, placebo-controlled study, 30 individuals with dyspepsia were given either 2.5 g daily of red pepper powder (divided up and taken prior to meals) or placebo for 5 weeks.13 By the third week of treatment, individuals taking red pepper were experiencing significant improvements in pain, bloating, and nausea as compared to placebo, and these relative improvements lasted through the end of the study.
All double-blind studies of topical capsaicin (or cayenne) suffer from one drawback: It isn’t really possible to hide the burning sensation that occurs during initial use of the treatment. For this reason, such studies probably aren’t truly double-blind. It has been suggested that instead of an inactive placebo, researchers should use some other substance (such as camphor) that causes at least mild burning. However, such treatments might also have therapeutic benefits; they have a long history of use for pain as well.
Because of these complications, the evidence for topical treatments cited below is less meaningful than it might at first appear.
Capsaicin cream is well established as a modestly helpful pain-relieving treatment for:
In a review of six randomized trials of 2,073 adults with postherpetic neuralgia or HIV-associated neuropathy, a high-dose capsaicin (8%) patch significantly improved pain symptoms for up to 12 weeks compared to a low-dose (0.04%) capsaicin patch.42
Supportive evidence also exists for the use of topical capsaicin for soft tissue pain (muscles, tendons, and ligaments)40 and pain following hernia repair.36 Weak evidence supports its use for fibromyalgia.4
Topical capsicum-based cream was associated with reduced acute low back pain compared to placebo in a small randomized trial with 40 adults.43 Actual cayenne rather than capsaicin has been tested for pain, as well. A 3-week, double-blind trial of 154 individuals with back pain found that cayenne applied topically as a “plaster” improved pain to a greater extent than placebo.30
A double-blind, placebo-controlled trial of nearly 200 individuals found that use of topical capsaicin can improve itching as well as overall severity of psoriasis.31 Benefits were also seen in a smaller double-blind study of topical capsaicin for psoriasis.32
One study of 208 patients with idiopathic (unknown cause) rhinitis found that using a capsicum nasal spray 3 times daily for 3 days (4 mcg/puff) may reduce symptom frequency.38 And, a small randomized, placebo-controlled trial involving 42 people with nonallergic rhinitis found that an intranasal product called Sinus Buster (a combination of cayenne and eucalyptus) used twice daily for 2 weeks helped to improve sinus congestion, pain, pressure, and headache.41
Capsaicin creams are approved over-the-counter drugs and should be used as directed. If the burning sensation that occurs with initial use is too severe, using weaker forms of the cream at first may be advisable.
For treatment of dyspepsia, cayenne may be taken at a dosage of 0.5 to 1.0 g three times daily (prior to meals).
Capsaicin creams commonly cause an unpleasant burning sensation when they are first applied; this sensation disappears over subsequent days as treatment is continued.
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23. Jensen PG, Larson JR. Management of painful diabetic neuropathy. Drugs Aging. 2001;18:737-749.
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Last reviewed December 2015 by EBSCO CAM Review Board Last Updated: 12/15/2015