Capsaicin
Capsicum annuum / Capsicum frutescens (source)
The heat compound in chili peppers, with strong evidence as a topical treatment for neuropathic and arthritis pain (it depletes the pain messenger substance P) and preliminary evidence for metabolism and appetite when taken orally.
At a Glance
- Best known for
- Topical relief of neuropathic pain (postherpetic neuralgia, diabetic neuropathy), Topical relief of osteoarthritis pain, Modest increase in energy expenditure and fat oxidation
- Evidence
- Strong
- Typical dose
- 0.025–0.075% cream applied 3–4x daily
- Type
- Compound
What is Capsaicin?
Capsaicin is the alkaloid that makes chili peppers hot. It is concentrated in the white pith around the seeds, and the heat of a pepper (its Scoville rating) is essentially a measure of its capsaicin content. In medicine capsaicin is a well-established topical pain reliever: low-concentration creams are sold over the counter for arthritis and nerve pain, and a prescription-strength 8% patch applied in clinics treats postherpetic neuralgia and diabetic foot pain. Orally, capsaicin and its milder cousins (capsinoids from sweet peppers) are studied for raising metabolic rate and curbing appetite. The paradox of capsaicin is that a compound that causes burning pain is used to relieve pain, which happens through a process called defunctionalization.
Known Health Benefits
How It Works
Capsaicin binds and opens TRPV1, the heat-and-pain receptor on sensory nerve endings, which is why it feels hot. With repeated or high-dose application, the nerve endings become overstimulated, deplete their stores of substance P (a neurotransmitter that carries pain signals to the spinal cord), and temporarily retract — a process called defunctionalization that can quiet pain for weeks to months. In the body, TRPV1 activation also triggers release of catecholamines, which increases energy expenditure, fat oxidation, and brown fat activity, and slows gastric emptying, which may reduce appetite. Capsaicin additionally stimulates gastric mucus secretion and blood flow, which is why in moderate amounts it is protective rather than harmful to the stomach lining.
What Research Says
Topical capsaicin has decades of controlled trial evidence. A 2017 Cochrane review of high-concentration (8%) capsaicin patches found moderate-quality evidence of pain relief in postherpetic neuralgia and HIV neuropathy and lower-quality evidence in diabetic neuropathy, with about 10% more people achieving substantial relief than with control. A 2004 BMJ systematic review of low-concentration creams (0.025–0.075%) found them moderately effective for neuropathic and musculoskeletal pain, with roughly one-third of users experiencing local burning. Osteoarthritis guidelines from several bodies list topical capsaicin as an option for knee and hand OA. The oral evidence is weaker: meta-analyses of capsaicinoid and capsinoid supplements find an increase in energy expenditure of about 50 kcal/day and a small reduction in appetite, which translates to minimal weight loss on its own. Observational studies associate frequent chili consumption with lower cardiovascular and all-cause mortality, but these cannot prove causation.
Active Compounds
Capsaicin and dihydrocapsaicin (capsaicinoids); milder non-pungent analogues called capsinoids in sweet peppers
Forms & Bioavailability
Topical capsaicin penetrates skin to reach nerve endings within hours but has minimal systemic absorption, so side effects stay local. Oral capsaicin is absorbed efficiently (over 90% in animals) and metabolized in the liver within hours. Enteric-coated or controlled-release capsules reduce stomach burning. Non-pungent capsinoids are converted to their active form in the gut and act on TRPV1 receptors there without causing a burning mouth, which makes them easier to take at effective doses. Tolerance to the burning sensation builds with regular use, but the metabolic effects also appear to diminish somewhat in habitual chili eaters.
Dosage Guidance
| Use Case | Dosage |
|---|---|
| Osteoarthritis / muscle pain (topical) | 0.025–0.075% cream applied 3–4x daily |
| Neuropathic pain (topical OTC) | 0.075% cream 3–4x daily |
| Postherpetic neuralgia / diabetic neuropathy | 8% patch, 30–60 min application every 3 months |
| Metabolism / appetite (oral) | 2–6 mg capsaicinoids or 3–9 mg capsinoids daily |
| Cayenne capsules | 30–120 mg cayenne 1–3x daily |
Always consult a healthcare provider for personalized dosing.
Natural Food Sources
- Chili peppers — cayenne, jalapeño, habanero, bird's eye, etc.
- Cayenne pepper powder and crushed red pepper
- Hot sauces and chili pastes
- Paprika (mild, low capsaicin)
- Sweet peppers (capsinoids, non-pungent)
Potential Side Effects
Topical: burning, stinging, redness at application site (usually fades after 1–2 weeks); oral: stomach pain, heartburn, flushing, sweating, diarrhea; cough if inhaled from cream
Who Should Avoid It
- Broken, irritated, or infected skin (topical use)
- Active peptic ulcer, severe GERD, or inflammatory bowel flare (oral use)
- Irritable bowel syndrome with diarrhea (oral capsaicin may trigger symptoms)
- Hemorrhoids or anal fissures (oral capsaicin can cause burning on elimination)
- Allergy to peppers or latex-fruit cross-reactivity
Pregnancy & Lactation
Chili peppers in food are safe during pregnancy and breastfeeding, though heartburn is common. Topical capsaicin creams are considered low-risk because systemic absorption is minimal, but should not be applied to the breast while nursing. Oral capsaicin supplements have not been studied in pregnancy and are best avoided.
Known Drug Interactions
May increase absorption of other topical drugs; oral capsaicin may enhance antiplatelet effects and theophylline absorption; ACE inhibitors may worsen capsaicin-related cough; may lower blood sugar additively
Evidence Classification
Supported by randomized controlled trials (RCTs), systematic reviews, or meta-analyses published in peer-reviewed journals.
Frequently Asked Questions
How can something that burns relieve pain?
Capsaicin initially activates pain nerves, which is the burning feeling, but repeated exposure exhausts their supply of substance P and temporarily disables the nerve endings. Once that happens — usually after 1–2 weeks of regular cream use, or within days of a high-dose patch — the nerves cannot transmit pain as effectively. This is why consistent application matters and why a single use does little.
Does eating spicy food boost metabolism?
Slightly. Controlled studies show capsaicin increases energy expenditure by around 50 calories a day and modestly reduces appetite, particularly for fatty and salty foods. Over a year this could add up to a kilogram or two if everything else stayed equal, but it is not a meaningful weight-loss strategy on its own. Regular chili eaters also become partly tolerant to this effect.
Is capsaicin bad for the stomach?
Contrary to old advice, moderate capsaicin does not cause ulcers and actually increases protective mucus and blood flow in the stomach lining; some studies show it reduces damage from aspirin and alcohol. However, it can worsen symptoms in people with existing ulcers, severe reflux, or IBS, and very high doses cause stomach pain and diarrhea.
What should I do if capsaicin cream gets in my eyes?
Rinse with cool water or saline for 15 minutes; it is intensely painful but not damaging. To prevent this, wear gloves or wash hands with soap and water (and ideally a little vegetable oil or dish soap, since capsaicin is oil-soluble) immediately after application. Do not apply cream before showering, exercising, or using a heating pad, as heat intensifies the burning.
References
- Systematic review of topical capsaicin for the treatment of chronic pain. Mason L, Moore RA, Derry S, Edwards JE, McQuay HJ. BMJ (2004)View study
- Topical capsaicin (high concentration) for chronic neuropathic pain in adults. Derry S, Rice AS, Cole P, Tan T, Moore RA. Cochrane Database Syst Rev (2017)
- Capsaicin topical. MedlinePlus. U.S. National Library of Medicine Drug Information (2023)
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This entry is for educational purposes only. It is not medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement regimen, especially if you take medications or have health conditions.