Capsaicin is the active component derived from the fruit of capsicum or cayenne pepper. It has been used in traditional medical systems as a remedy to relieve muscle and arthritic pain and to treat cluster headaches and psoriasis. For these purposes, capsaicin is an active ingredient in some topical creams and nasal sprays. It is also available in a prescription-strength patch. Oral formulations are marketed largely for digestive and circulatory problems, poor appetite, and weight loss. (See Cayenne Pepper)

Studies support benefits of topical low-concentration capsaicin formulations for psoriasis ⁽¹⁾, prurigo nodularis ⁽²⁾, and pruritus ani ⁽³⁾. It is also conditionally recommended for osteoarthritis  ⁽⁴⁾, and a meta-analysis suggests it may be as effective as topical NSAIDs for osteoarthritic pain ⁽⁴⁴⁾, but its utility for rheumatoid arthritis remains inconclusive ⁽⁵⁾. An older clinical trial shows capsaicin 0.075% cream may control post-surgical pain in cancer patients ⁽⁶⁾. A case report in a palliative care patient using capsaicin 0.025% for opioid-refractory upper extremity pain also reported benefit ⁽⁷⁾.

A high-concentration dermal capsaicin patch was shown safe and effective for postherpetic neuralgia ⁽⁸⁾, and was approved for prescription use. Data also suggest it is superior to pregabalin ⁽⁴⁵⁾, and effective for diabetic peripheral neuropathy ⁽³⁶⁾, heterogenous neuropathic pain ⁽³⁷⁾, and neuropathic pain arising from radiculopathies ⁽³⁸⁾, but not HIV-associated neuropathic pain ⁽⁹⁾. A recent systematic review cites some benefit for both postherpetic neuralgia and HIV-neuropathy over controls. However, the patch is best used when other therapies have failed due to the small number of patients who may benefit (1 in 8) and unknown risks ⁽¹⁰⁾. Low-concentration capsaicin was determined as unlikely to have meaningful use for these conditions in clinical practice ⁽¹¹⁾. Data are also limited in patients with post-mastectomy neuropathy ⁽¹²⁾.

A preliminary study suggests improved swallowing function in elderly patients with dysphagia when 0.025% capsaicin ointment was applied to the external auditory canal ⁽⁴³⁾. In other reports, several case series suggest topical capsaicin can be effective for cannabis-associated hyperemesis ^(39) (42). Only a few small studies suggest intranasal capsaicin of divergent formulations may be helpful for rhinitis ^(13) (14), and its effectiveness for cluster headaches is unknown ⁽¹⁵⁾.

There is continued controversy over whether capsaicin acts as a carcinogen, co-carcinogen, or anti-carcinogen ^{(16) (17) (18)}. For example, capsaicin has demonstrated chemopreventive and antiproliferative effects against various cell lines including breast ⁽¹⁹⁾, bladder ⁽²⁰⁾, prostate cancer cells ⁽²¹⁾. Also, a small study suggests utility of a high-concentration dermal capsaicin patch in relieving pain associated with chemotherapy-induced peripheral neuropathy (CIPN) ⁽⁴⁰⁾. However, long-term topical application was shown to increase skin carcinogenesis in mice treated with a tumor promoter ⁽¹⁸⁾, although such effects may be concentration-dependent ⁽²²⁾. Therefore, more studies are needed to clarify the roles of capsaicin in relationship to cancer.