The chemical compound capsaicin (8-methyl-N-vanillyl-6-nonenamide) is the active component of chilli peppers (Capsicum). It is an irritant for mammals including human and produces an illusion of burning in the mouth. Capsaicin is produced as a secondary metabolite by certain plants of the genus Capsicum (red peppers), probably as deterrant againsts herbivores. Pure capsaicin is a lipophilic colorless waxy compound.

Capsaicin is the main member of the group of capsaicinoids, which are present in different amounts in different species. This accounts for the delayed reaction to C. chinense (habanero) as compared to other species.

• trans-8-methyl-N-vanillyl-6-nonenamide (capsaicine)
• 8-methyl-N-vanillyl-nonamide (dihydrocapsaicin)
• 7-methyl-N-vanillyl-octamide
• 9-methyl-N-vanillyl-decamide
• trans-9-methyl-N-vanillyl-7-decenamide

Food: Because of the burning sensation capsaicin is commonly used in food products to give them added spice or "heat" (piquancy). The degree of heat found within a food is measured on the Scoville scale. Typically the capsaicin is obtained by using chili peppers as the source. Another common source is hot sauces (which may contain pure capsaicin or chile peppers). These sources are preferred over pure capsaicin for reasons of safety resulting from the lower concentration. Capsaicin is fat-soluble rather than water-soluble, so the drinking of water offers little relief from the burning sensation of excessively spiced food. Consuming unspicy fatty food or beverages (buttered bread, ice cream, milk etc.) will extract the residual capsaicin from the mouth and relieve the burning.

Medical: Capsaicin is used in topical ointments used to relieve the pain of peripheral neuropathy (for example post-herpetic neuralgia). The treatment typically involves the application of a topical anesthetic until the area is numb. Then the capsaicin is applied by a therapist wearing rubber gloves and a face mask. The capsaicin remains on the skin until the patient starts to feel the heat at which point it is promptly removed. The result appears to be that the nerves are overwhelmed from the burning sensation and are unable to report pain for an extended period of time. Ointments and balms for the relief of aching muscles often contain capsaicin in the form of a chili oil extract, listed amongst the ingredients under such names as "capsic. oleo. res."

Non-lethal force: Capsaicin is also the active ingredient in the chemical riot control agent pepper spray. When the spray comes in contact with skin, especially eyes or mucous membranes it is very painful. Refer to the Scoville scale for a comparison of pepper spray to other sources of Capsaicin. In large quantities, capsaicin can be a lethal poison. Symptoms of overdose include difficulty breathing, blue skin, and convulsions. While the large amount needed to kill an adult human being and the low concentration of capsaicin in chiles make accidental poisioning by chile consumption exceedingly unlikely, capsaicin has been implicated in some cases of infanticide in India.

The burning and painful sensations associated with capsaicin result from capsaicin's chemical interaction with sensory neurons. Capsaicin, as a member of the vanilloid family, binds to a receptor called the vanilloid receptor subtype 1 (VR1) first cloned in 1997, VR1 is an ion channel-type receptor. VR1, can also be stimulated with heat and physical abrasion, permits positively-charged ions (i.e. cations) to pass through the cell membrane and into the cell from outside when activated. The resulting "depolarization" of the neuron stimulates it to signal the brain. By binding to the VR1 receptor, the capsaicin molecule produces the same effect that excessive heat or abrasive damage would cause, explaining why the spiciness of capsaicin is described as a burning sensation.

The VR1 ion channel has subsequently been shown to be a member of the superfamily of TRP ion channels, and as such is now refer to as TRPV1. There are a number of different TRP ion channels that have been shown to be sensitive to different ranges of temperature and probably are responsible for our range of temperature sensation. Thus, capsaicin does not actually cause a chemical burn; it causes only the sensation of one.

A euphoric sensation caused by the consumption of large quantities of capsaicin from capsaicin laden foods. It's theorized that the pain induced by capsaicin causes the human body to release endorphins. Eventually, enough are released to create a sensation that is frequently compared to "runner's high."

The "heat" of chile peppers is measured in Scoville units. Bell peppers rank at zero Scoville units, jalapeños at 3,000–6,000 Scoville units, and habaneros at 300,000 Scoville units. The record for the highest number of Scoville units in a pepper is assigned by the Guinness Book of Records to the Red Savina Habanero, measuring 577,000 units. However, a recent report was made of a pepper from India called the Naga Jolokia measuring at 855,000 Scoville units. Both the Red Savina and the Naga Jolokia claims are disputed as to their validity, and lack independent verification. Pure capsaicin rates at 16,000,000 Scoville units.

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It uses material from the Wikipedia article "Capsaicin".