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 againstulcerscaused 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 addition, it appears that, contrary to long standing belief, hot peppers do not cause increased pain in people with hemorrhoids.34