Cayenne Pepper (Capsicum annuum / Capsicum frutescens)
1. Identity: Botanical Classification, Chemistry, and Common Forms
Botanical and Chemical Names
Cayenne pepper (Capsicum annuum) is a small-fruited pepper and the source of a very pungent spice of the same name. It is one of many chili pepper cultivars of Capsicum annuum and is said to have originated in Cayenne, French Guiana. There is, however, nomenclatural overlap in the literature: Capsicum spices are produced from the dried fruits of the genus Capsicum (Solanaceae). Cayenne pepper and red pepper are two synonyms of Capsicum frutescens, whereas paprika or chili is derived from Capsicum annuum. Capsicum has been officially defined in the USP 23 as the dried ripe fruit of Capsicum frutescens Linne or Capsicum annuum Linne.
The genus Capsicum is a member of the large tropical family Solanaceae. There are numerous species, of which Capsicum annuum, Capsicum chinense, and Capsicum frutescens are closely related. Common synonyms and vernacular names include bird pepper, red pepper, chili pepper, Guinea spice, and pimento. The spice is produced by drying and grinding the orange to deep-red fruits and derives its pungent flavor from the chemical capsaicin.
Scoville Rating
Cayenne pepper, quite hot to human taste, is approximately 30,000 to 50,000 units on the Scoville scale. This places it well above mild chili varieties but well below habanero and related ultra-hot cultivars.
Common Forms and Preparations
Cayenne is encountered in multiple forms as a dietary supplement and in pharmaceutical preparations:
- Dried powder: Capsicum is the dry powder obtained by grinding up the fruits of these plants.
- Oleoresin: Capsicum oleoresin (or capsaicin oleoresin) is the liquid concentrate extracted from the dry powder. Capsaicin, a white crystalline material, is obtained from the liquid concentrate.
- Oral capsules: Capsaicin-containing supplements are usually sold in the form of dried chili pepper powder (e.g., cayenne). A capsule containing 500 mg of dried cayenne pepper contains around 1.2 mg of capsaicin.
- Topical preparations: Capsaicin is administered in many forms such as low-concentration creams, lotions, patches, intradermal injections, oral formulations, subcutaneous injections, intravenous, films, microemulsions, liposomes, and nanotechnology-derived drug delivery systems.
- High-concentration patch: The US Food and Drug Administration has granted approval of a capsaicin dermal analgesic patch, which is also authorized in the EU to manage peripheral neuropathic pain in adults, either as a monotherapy or in conjunction with other therapeutic agents.
2. Traditional and Historical Use
Pre-Columbian and Indigenous Americas
The plant known today as cayenne pepper (Capsicum annuum) is named after the city of Cayenne in French Guiana, but its roots reach much deeper into the cultural traditions of pre-Columbian peoples. Archaeological evidence shows that chili peppers were ground, dried, and used as seasoning or paste in daily cooking, long before salt or black pepper became common. Indigenous healers used it to treat sore throats, digestive issues, wounds, and fevers. The Aztecs believed chili peppers gave strength and vitality, and cayenne was sometimes used in rituals and offerings to the gods.
Indigenous peoples, including the Arawaks and the Mayans, were among the first to cultivate and use this potent spice. Native Americans used cayenne as a food preservative and for medicinal purposes, including pain relief and respiratory conditions.
Introduction to Europe and Global Spread
In 1493, Christopher Columbus, on his first return voyage from the New World, introduced chili peppers to Europe. Mistaking them for a relative of black pepper (then a highly prized spice from India), Columbus called them "peppers" due to their pungency — a name that stuck. From Europe, the spice spread rapidly along trade routes to Africa, Asia, and beyond. Both fresh cayenne peppers and the spice derived from them are used extensively in Creole and Cajun cooking in the United States and in the cuisines of Mexico, Italy, and China as well as throughout much of Southeast Asia.
Traditional Medicinal Systems
Cayenne's appeal was not limited to taste alone. In traditional medicine, especially in Ayurveda and Traditional Chinese Medicine, cayenne has long been used to aid digestion, improve circulation, and relieve pain. Indigenous peoples have used cayenne for its stimulating and digestive properties for thousands of years. Traditional Chinese Medicine (TCM) has also used cayenne for thousands of years to improve circulation and treat digestive problems. Cayenne has been incorporated in Ayurveda to aid digestion and as a circulatory stimulant.
Historically, cayenne has been used for treating a variety of health issues, including digestion problems, muscle pain, joint pain, and as a circulatory stimulant. It has been believed to have anti-inflammatory and analgesic properties. Due to its antimicrobial properties, cayenne pepper has also been used to preserve food.
In European traditional medicine, a galenic rubefacient tradition also developed. A galenic preparation composed of rubefacient substances of vegetable origin, which generated vasodilation and increase in blood circulation on the treated areas, was first prescribed in 1909 by Dr. Giuseppe Munari to treat pain of various areas of the locomotive system. He proposed a method based on applications prepared according to his own galenic formula that became famous across Italy and Europe.
3. Key Constituents and Active Compounds
Capsaicinoids
Capsaicin (8-methyl N-vanillyl-6-noneamide) is the main pungent principle of hot green and red peppers. There are two main capsaicinoids — capsaicin and dihydrocapsaicin — and three minor capsaicinoids: nordihydrocapsaicin, homocapsaicin, and homodihydrocapsaicin. Twenty-three capsaicinoid analogs have been described. These include capsaicin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, homocapsaicin, norcapsaicin, and nornorcapsaicin. Capsaicin and dihydrocapsaicin constitute approximately 90% of these compounds in pepper.
Capsaicin (N-Vanillyl-8-methyl-6-(E)-noneamide) is the most pungent of the capsaicinoids. It is very soluble in fats, oils, and alcohols. Capsicum also contains a red coloring matter, oleic acid, palmitic acid, and stearic acid.
Carotenoids and Other Phytochemicals
Capsicums contain natural resins, particularly the terpene capsanthin, which is the carotenoid responsible for the orange-red color associated with ripe chili peppers. Peppers (Capsicum annuum L.) are an important crop usually consumed as food or spices. They contain a wide range of phytochemicals, such as capsaicinoids, phenolics, ascorbic acid, and carotenoids. Additional compounds present include flavonoids and vitamins A, C, and E.
4. Mechanisms of Action
TRPV1 Receptor Activation
By acting on the capsaicin receptor or transient receptor potential cation channel vanilloid subfamily member 1 (TRPV1), capsaicin selectively stimulates and, in high doses, defunctionalizes capsaicin-sensitive chemonociceptors with C and Aδ afferent fibers. This channel, which is involved in a wide range of neuronal processes, is expressed in peripheral and central branches of capsaicin-sensitive nociceptive neurons, sensory ganglia, the spinal cord, and different brain regions in neuronal cell bodies, dendrites, astrocytes, and pericytes.
TRPV1 is a homotetrameric membrane protein combining a transmembrane pore with domains devoted to vanilloid, thermal, and proton stimuli — each capable of triggering channel gating. This single protein provides integral, polymodal transduction via ion channel activation. TRPV1 senses various noxious stimuli in primary sensory neurons, leading to pain perception through the generation of action potentials upon the activation of voltage-gated sodium channels. Mammalian TRPV1 is activated by noxious heat, acid, and many chemical compounds including capsaicin.
Neuropeptide Release and Neurogenic Inflammation
Activation of sensory nerves by capsaicin evokes the local release of the neuropeptides calcitonin gene-related peptide (CGRP), the tachykinins substance P (SP) and neurokinin A (NKA), and somatostatin not only into the spinal cord but also in the periphery. Activation of TRPV1 on the terminal endings of the sensory fibers produces a calcium and sodium influx that ultimately results in the release of a cocktail of neuropeptides. Among these, the tachykinins substance P and neurokinin A (NKA) and the calcitonin-gene-related-peptide (CGRP) are of particular relevance. Epithelial, endothelial and smooth muscle cells, as well as resident immune cells, respond to these neuropeptides and give rise to a complex series of events collectively referred to as neurogenic inflammation.
Desensitization (Defunctionalization)
Capsaicin functions to activate and then, at higher doses and over time, desensitize this class of neurons. This latter response, by a process known as tachyphylaxis, provides the basis for the therapeutic interest in capsaicin. Defunctionalization is due to a number of effects that include temporary loss of membrane potential, inability to transport neurotrophic factors leading to altered phenotype, and reversible retraction of epidermal and dermal nerve fibre terminals. Capsaicin selectively activates TRPV1, a Ca²⁺-permeable cationic ion channel that is enriched in the terminals of certain nociceptors. Activation is followed by a prolonged decreased response to noxious stimuli.
Thermogenic and Metabolic Mechanisms
Activation of TRPV1-expressing neurons in the digestive tract sends a signal to the brain via the vagal nerve; this in turn evokes an activation of sympathetic neurons that is selective for brown fat. Many clinical trials have evaluated the impact of capsaicin ingestion on metabolic rate, respiratory quotient, and appetite; these conclude that capsaicin can modestly enhance energy expenditure, while boosting fat oxidation (lower RQ) and diminishing appetite — effects conducive to weight control. Dietary capsaicin also stimulates glucagon-like peptide-1 (GLP-1) secretion in the gastrointestinal tract.
Cardiovascular Mechanisms
Emerging evidence suggests that TRPV1 plays a critical role in the regulation of cardiovascular function and metabolic homeostasis. Activation of TRPV1 by its specific agonist capsaicin promotes endothelium-dependent vasodilation and subsequently contributes to lower blood pressure. However, the direct impact of capsaicin on vascular smooth muscle is to provoke constriction, owing to increased calcium influx. Hence, the net impact of capsaicin on vascular tone and blood pressure may reflect complex interactions and countervailing effects.
Platelet and Anticoagulant Effects
Capsaicin inhibits platelet aggregation, potentially by altering the fluidity of the platelet membrane. This mechanism appears to be independent of TRPV1 because the effects are not inhibited by a competitive TRPV1 inhibitor. On the other hand, capsaicin has also been shown to promote platelet aggregation through a mechanism dependent on TRPV1. In that mechanism, TRPV1 may induce release of serotonin to drive platelet activation in response to adenosine diphosphate and thrombin. This dual and potentially conflicting effect on platelet function means the net anticoagulant impact is not well characterized in humans.
5. Scientific Evidence by Area of Use
5.1 Pain Relief — Topical Application
Topical capsaicin has the most developed clinical evidence base of any indication, and it has achieved regulatory approval as a prescription pharmaceutical in high-concentration form.
Low-concentration creams (0.025%–0.075%): A systematic review pooling randomized controlled trials assessed the efficacy of topically applied capsaicin for chronic pain from neuropathic or musculoskeletal disorders. Six double-blind placebo-controlled trials (656 patients) were pooled for analysis of neuropathic conditions. The relative benefit from topical capsaicin 0.075% compared with placebo was 1.4 (95% confidence interval 1.2 to 1.7) and the number needed to treat was 5.7 (4.0 to 10.0). The overall conclusion was that although topically applied capsaicin has moderate to poor efficacy in the treatment of chronic musculoskeletal or neuropathic pain, it may be useful as an adjunct or sole therapy for a small number of patients who are unresponsive to, or intolerant of, other treatments.
High-concentration patch (8%): The Cochrane Collaboration has specifically reviewed high-concentration (8%) capsaicin patches for chronic neuropathic pain. Reviews searched for evidence from controlled trials on the efficacy and tolerability of topically applied, high-concentration (8%) capsaicin in chronic neuropathic pain in adults, using randomized, double-blind, placebo-controlled studies of at least 6 weeks' duration using high-concentration (5% or more) topical capsaicin. Capsaicin is approved as a topical treatment of neuropathic pain. The analgesia lasts for several months after a single treatment. The US FDA has granted approval of a capsaicin dermal analgesic patch, which is also authorized in the EU to manage peripheral neuropathic pain in adults, either as a monotherapy or in conjunction with other therapeutic agents. The patch has demonstrated both safety and efficacy in managing neuropathic pain.
Injectable capsaicin: Interest also exists in the use of injectable capsaicin as a treatment for focal pain conditions, such as arthritis and other musculoskeletal conditions. Injection of capsaicin showed therapeutic efficacy in patients with Morton's neuroma, a painful foot condition associated with compression of one of the digital nerves. The relief of pain was associated with no change in tactile sensibility. Though injection evokes short-term pain, the brief systemic exposure and potential to establish long-term analgesia without other sensory changes create an attractive clinical profile.
Osteoarthritis: A systematic review concluded that capsaicin cream is a safe and effective treatment for arthritis and that mean reductions in pain were statistically significant compared with those reported with placebo. The studies included evaluated concentrations of either 0.025% or 0.075% topical capsaicin, or 11 mg capsinoid capsicum plaster, with or without concomitant oral analgesics.
Fibromyalgia: Small studies have examined various natural products — such as topical creams containing capsaicin — for fibromyalgia. Evidence in this area is regarded as preliminary.
Overall evidence rating for topical analgesia: Strong (at the 8% concentration, FDA-approved); moderate at low concentrations for arthritis and neuropathy; insufficient for fibromyalgia.
5.2 Thermogenesis, Weight Management, and Metabolic Effects
The outcomes of earlier trials are controversial concerning the effect of capsaicinoids/capsinoids on thermogenesis. A systematic review and meta-analysis was carried out to examine the effect of capsaicinoids/capsinoids on thermogenesis indices including resting metabolic rate (RMR) and respiratory quotient (RQ) in healthy adults. Of 4,092 articles, 13 studies were included in the meta-analysis. Pooled effect sizes revealed that compared with placebo, capsaicinoids/capsinoids significantly increased RMR (WMD: 33.99 kcal/day, 95% CI: 15.95, 52.03; I²: 0%, p = .94), energy expenditure, and fat oxidation.
A separate systematic review and meta-analysis specifically on weight loss outcomes among overweight and obese subjects identified 15 studies from 2,377 retrieved studies, ultimately including 15 RCTs with 762 individuals. A further meta-analysis on energy intake concluded that daily consumption of capsaicinoids may contribute to weight management through reductions in energy intake. There may be potential for capsaicinoids to be used as long-term, natural weight-loss aids, but further long-term randomized trials are needed to investigate these effects.
A critical meta-analysis synthesizing thermogenic and appetitive outcomes concluded that capsaicin and capsiate both augment energy expenditure and enhance fat oxidation, especially at high doses. Furthermore, the balance of the literature suggests that capsaicin and capsiate suppress orexigenic sensations. The magnitude of these effects is small. More specifically, purposeful inclusion of these compounds in the diet may aid weight management, albeit modestly.
One specific double-blind study with capsiate (9 mg daily for 12 weeks) found that the capsiate group, on average, lost 0.4 kg of weight and 1 cm of waist girth beyond that achieved with placebo — not an effect of much practical importance unless it persists and increases over time.
The effects of capsaicin or capsiate on thermogenesis are most notable in humans bearing detectable amounts of brown fat; however, there is some evidence that prolonged ingestion of these agents may lead to recruitment of brown fat in humans. These effects on thermogenesis are modest in magnitude; there do not appear to be any reports of clinically significant hyperthermia with ingestion of capsaicin or capsiate.
Overall evidence rating for weight/metabolic effects: Statistically significant but clinically modest thermogenic effects are supported by multiple RCTs and meta-analyses. Evidence for meaningful long-term weight loss in humans is weak; findings are strongest for acute thermogenesis and energy expenditure.
5.3 Cardiovascular Effects
Different studies have indicated that red pepper and its active constituent capsaicin have therapeutic potential in different components of metabolic syndrome. Reviews have summarized animal and human studies on the effect of red pepper and capsaicin on hypertension, high blood glucose, obesity, and dyslipidemia.
Capsaicin feeding has shown an antihypertensive effect in rats genetically prone to hypertension, and this compound also blunts the nocturnal rise in blood pressure or development of hypertension in mice fed a high salt diet. Improved nitric oxide (NO) function may underlie these effects. In humans, endothelial TRPV1 activation by dietary capsaicin promoted vasodilation and reduced blood pressure in genetically hypertensive rats, though this is animal data. Human clinical evidence for blood pressure lowering remains limited.
A 2022 review concluded that although a chili pepper-rich diet is associated with a reduced risk of dying due to cardiovascular disease, dietary capsaicin has no clear effect on blood glucose or lipid profiles. The reduced mortality risk may therefore reflect the beneficial action of digested capsaicin on gut microbiota.
The potential role of capsaicin in glucose homeostasis has been validated in animal experiments, although evidence for capsaicin regulating glucose metabolism in humans is relatively limited.
Overall evidence rating for cardiovascular effects: Largely preclinical and observational. Animal studies are promising; consistent, well-powered human RCTs demonstrating clinically meaningful effects on blood pressure, lipids, or glucose are lacking.
5.4 Gastrointestinal Effects
TRPV1 is expressed in gastric epithelial cells, where it stimulates the secretion of gastrin. Previous studies have attributed several positive gastrointestinal effects to capsaicin: it induces the release of calcitonin gene-related peptide, activates gastroprotective cyclooxygenase-1, and increases the absorptive surface of the small intestine. However, a number of studies have suggested that prolonged exposure to high doses of capsaicin can harm the gastrointestinal tract. Exploring the minimum effective doses required to achieve the desired therapeutic effects while minimizing potential side effects is necessary for enhancing the clinical utility of capsaicin-based treatments.
Capsaicin can stimulate saliva and digestive enzymes of the pancreas and small intestine. A clinical trial of red pepper for functional dyspepsia (Bortolotti et al., Aliment Pharmacol Ther 2002) has been referenced in the literature as evidence for symptomatic improvement in this condition.
Overall evidence rating for gastrointestinal effects: Preliminary. Both gastroprotective and gastrointestinal-irritant effects have been documented depending on dose and duration; definitive human RCT evidence for specific GI conditions is limited.
5.5 Nasal and Respiratory Applications
Topically applied capsaicin is used in migraine, trigeminal neuralgia, herpes zoster, chronic musculoskeletal pain, and skin disorders. Intranasal capsaicin has been studied for allergic rhinitis. Several experimental and clinical studies provided evidence that capsaicin protected against ischemic or excitotoxic cerebral neuronal injury and may lower the risk of cerebral stroke. This area, however, largely remains experimental.
6. Body Systems Associated with Cayenne Pepper / Capsaicin
- Nervous system (pain pathways): TRPV1-mediated activation and desensitization of nociceptive C-fibres and Aδ fibres; approved pharmaceutical use for neuropathic pain.
- Musculoskeletal system: Topical use for osteoarthritis, rheumatoid arthritis, and musculoskeletal pain conditions.
- Cardiovascular system: Endothelial TRPV1 activation, potential effects on vascular tone, blood pressure regulation, and platelet function.
- Metabolic/endocrine system: Brown adipose tissue activation, thermogenesis, GLP-1 secretion, and potential effects on glucose homeostasis.
- Gastrointestinal system: Effects on gastric secretion, digestive enzyme stimulation, gut microbiota modulation, and gastroprotective mechanisms.
- Respiratory system: Potential nasal decongestant and antiallergic rhinitis effects via sensory neuron desensitization; dual role as a respiratory irritant at high exposures.
- Integumentary system (skin): Topical rubefacient and analgesic preparations; dermatological investigations.
7. Dosage Forms and Dosages Reported in Studies
Dosages vary substantially by formulation, indication, and whether the active measurement is expressed as capsaicin content, Scoville units, or total pepper weight. The following are dosages as reported in cited sources:
- Dried cayenne pepper capsules (oral): Capsaicin-containing supplements are usually sold as dried chili pepper powder. A capsule containing 500 mg of dried cayenne pepper contains around 1.2 mg of capsaicin.
- Capsaicin in acute thermogenesis studies: Capsaicin was given at a dose of 2.56 mg (equivalent to 1.03 g of red chili pepper, 39,050 Scoville heat units) with every meal in one placebo-controlled crossover study.
- Capsiate (non-pungent analogue) for weight/fat studies: Supplementation with capsiate at 9 mg daily for 12 weeks was used in one double-blind study.
- Low-concentration topical creams: The included studies in one systematic review evaluated either 0.025% or 0.075% topical capsaicin, or 11 mg capsinoid capsicum plaster, applied 3–4 times daily.
- High-concentration topical patch: The FDA-approved pharmaceutical patch is standardized at 8% capsaicin; in one large trial, ~10% of patients reported adverse drug reactions, the most frequent of which were erythema and pain at the application site.
- Capsaicin supplement potency range: Capsaicin supplements are typically derived from cayenne peppers. These supplements commonly use Scoville heat units to measure potency. The typical range is 40,000–100,000 SHU, though because they are in a capsule, you do not experience the same heat on your tongue as when you eat hot peppers.
8. Safety Considerations and Drug Interactions
Topical Adverse Effects
The more common potential adverse reactions and events with topical patch administration include local erythema, local pain, local pruritus, local edema, local swelling, local dryness, hypertension, papules, pruritus, nausea, vomiting, nasopharyngitis, sinusitis, and bronchitis. The more rare complications include abnormal skin odor, cough, dizziness, dysgeusia, headaches, hypesthesia, peripheral edema, peripheral sensory neuropathy, and throat irritation. Around one third of patients experienced local adverse events with capsaicin that would not have been the case with placebo.
Mucous Membrane and Ocular Exposure
Capsaicin is a potent irritant, and if exposed to the mucous membranes, it can cause severe irritation, pain, and burning. When it gets in the eye, capsaicin can cause prolonged burning pain with tearing, photophobia, and blurry vision. When inhaled, it can cause dry coughing spells, wheezing, and dyspnea.
Gastrointestinal Safety at High Oral Doses
Although the pain and burning from consumption of cayenne or capsaicin can be disturbing, no actual harm results from its consumption at culinary doses. However, a number of studies have suggested that prolonged exposure to high doses of capsaicin can harm the gastrointestinal tract. Exploring the minimum effective doses required to achieve the desired therapeutic effects and minimizing the potential side effects are quite necessary for enhancing the clinical utility of capsaicin-based treatments.
Cardiovascular Caution with High Supplemental Doses
Some people who have used capsaicin to lose weight have presented to the emergency department with profuse diaphoresis and chest pain. In these patients, reports of myocardial ischemia have been reported. This highlights that high-dose supplemental use carries risks distinct from normal dietary intake.
Asthma
Some studies have reported relative contraindications in patients with asthma, as they have greater sensitivity to capsaicin. It is presumed that there is increased TRPV1 activity in asthmatics with an increase in endovanilloids in the airways.
Drug Interactions
- ACE inhibitors: Capsaicin — which makes foods like peppers spicy — can sometimes worsen an ACE inhibitor-related cough. This interaction is documented in the clinical literature, with topical capsaicin having been reported to induce cough in a patient receiving an ACE inhibitor.
- Anticoagulants/antiplatelets: Oral capsaicin should be avoided with anticoagulants like warfarin and antiplatelets such as aspirin, as it can increase the risk of bleeding. This is biologically plausible given the documented dual effects of capsaicin on platelet function noted above.
- Diabetes medications: Capsaicin can interact with several medications, including blood thinners, ACE inhibitors, and diabetes drugs. Potential additive effects on blood glucose lowering warrant caution.
Systemic Absorption from Topical Use
Systemic absorption from topical capsaicin is unlikely, hence topical application is not expected to cause serious adverse effects. Significant systemic absorption is unlikely to cause adverse effects in the fetus. Significant systemic absorption of capsaicin topical application is unlikely to appear in breast milk.
General Tolerability Note
Capsaicin, which is abundant in chili peppers, exerts antioxidative, antitumor, antiulcer, and analgesic effects and has demonstrated potential as a treatment for cardiovascular, gastrointestinal, oncological, and dermatological conditions. Unique among natural irritants, capsaicin initially excites neurons but then "calms" them into long-lasting non-responsiveness. The clinical usefulness of capsaicin is limited by its short half-life.
References
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