Cayenne

Derived from the fruit of Capsicum, cayenne is among the most widely consumed culinary spice. Traditionally, it is used topically as a rubefacient, as a gargle for laryngitis and orally as a gastrointestinal stimulant. The active component, capsaicin, is an irritant which has been used in scientific studies to evaluate pain sensation.
Phytochemical extracts of capsicum have been shown to exhibit more antioxidant activity than broccoli, carrot or spinach ⁽³⁾. Topical capsaicin cream may be effective against chronic soft tissue pain ⁽²²⁾ and low back pain ⁽¹³⁾. Capsaicin may also increase insulin and decrease blood glucose levels ⁽¹⁴⁾. Supplementation with capsicum for burning mouth syndrome is associated with significant side effects ⁽⁴⁾.

In vitro studies have shown that capsaicin has cytotoxic effects against multidrug resistant lymphoma ⁽⁵⁾, oral tumor cell lines ⁽⁶⁾ and inhibits leukemia cell growth ⁽⁷⁾. Topical capsaicin may alleviate oral mucositis pain associated with chemotherapy and radiation therapy ⁽⁸⁾. Capsaicin cream has also been shown effective in reducing post-surgical pain in cancer patients ⁽⁹⁾ and for treating psoriasis ^{(10) (11)} and pruritus ⁽¹²⁾.

Use of gloves is recommended when applying topical capsaicin. An adverse effect of topical administration is burning following contact with moist mucous membranes ^{(1) (2)}.
Toxicities following overdoses from oral injestion include gastroenteritis and renal damage ⁽¹⁵⁾. There are reports of erythematous dermatitis formed in infants subsequent to breast-feeding from mothers who had ingested food flavored with red pepper ⁽¹⁶⁾. Administration of even a single dose of capsicum may interfere with theophylline metabolism ⁽¹⁷⁾.