Can you tell me if capsaicin creams that I keep seeing in my drugstore work for pain? All I know is that peppers burn my skin! Why would people put this on their skin? How is it supposed to work? I am scared to try it until I know how it works.
S. L. A., Georgia
You are very wise to want to know how something works before you try it!! Your curiosity can save you. I hope your curiosity is contageous!
Red pepper creams do indeed work for some kinds of pain. Isn't that remarkable? In a nutshell, they are thought to work by quickly depleting your nerves of a pain signaling molecule called substance P. As one of my pharmacology students once neatly put it, "It's a substance P dumper". The real trick is to not use too much of it or to apply it to any sensitive parts!
Here is more detail on red pepper, from my book:
Capsicum annum or Capsicum frutescens
History and Folklore Also called capsicum, chili pepper, and cayenne pepper, red pepper is a member of the Solanaceae family of plants, and is native to South America. (Black pepper is an unrelated plant from Africa.) The ancient version of these peppers was small, spicy berries. As early as 7000 BCE, South American Indians, perhaps on the basis of a dare, started using them in cooking. Until European explorers brought this tropical plant to India, Africa, China, and Indonesia, the traditionally hot meals of these countries did not include red pepper, which is difficult to imagine.
Different cultures developed new varieties, from the mild Hungarian pepper (paprika) to the fiery South American Habanero. Botanists have recorded over 90 varieties.
Think about the difference between the customary foods of hot and cold countries. The spiciest meals are in the hottest countries, but why?
Some say spicy food helped residents sweat, cooling them off. Yet sweating doesn’t normally require encouragement in heat. The habit of adding plants with violent tastes to food was much more likely a means of preserving it without refrigeration. Food refrigeration using methods prior to refrigerators—ice and cold running streams—wasn’t much of an option in the tropics. The only other convenient means of preserving food is to dump some spicy antibacterial herbs into it. Most spices’ pungent oils are manufactured by plants to keep microbes from attacking the plant, so the antibacterial activity of herbal oils is widespread (but usually too nonspecific to pay much attention to.) The presence of abundant red pepper and other spices discouraged the growth of bacteria, at the risk of discouraging the diner. There was an added benefit: Should the spices fail to retard spoilage, they could still mask a rotten taste.
Red pepper was also used to relieve indigestion and gas, to relieve sinus congestion, headache, and muscle pain. It also has a reputation of being an aphrodisiac (but don’t try it for that use topically, it will probably backfire.)
What’s in it Red pepper oil contains capsaicinoids, alkaloids that resemble vanillin from vanilla, oddly enough, yet an 8-10-carbon hydrocarbon is tacked on to the completely reduced aldehyde carbon of vanillin using an amide linkage. Most of these are capsaicin (32-38%) and dihydrocapsaicin (18-52%). The carotenoid pigments include carotene, capsanthin, alpha-carotin, and violaxanthine. Apiin and luteolin glycoside are the major flavonoids, and the mixture of steroid saponins in the seeds are collectively called capsicidine. The pepper also has a significant amount of vitamin C.
How Scientists Think it Works
Even without taste buds, red pepper would still burn your mouth. When you eat red pepper, you do not actually taste capsaicin with your taste buds. Like other oil-soluble, small molecules, it has the ability to penetrate tissues. It slowly moves through tissues in your mouth, to trigger deeper nerves, and the classic burning sensation slowly grows. Since humans can detect one part per million, a little bit goes a long way.
Paradoxically, it relieves pain, but it isn’t your usual counterirritant. This painful plant is used topically very carefully for pain relief, and it seems to work. At first scientists provided the classic old “counterirritant theory” to explain why: you are so distracted by the pain caused by the herb that you forget your original pain. This is sort of like hitting your thumb with a hammer so you can forget your headache, and you can imagine how appealing this sort of treatment is once someone grasps how it works. Some counterirritant action may in part explain how red pepper works. However, experimenters have unearthed a far more promising mechanism.
The capsaicin in red pepper fools your brain into sensing heat when there isn’t any. Acting just like one of your own neurotransmitters, capsaicin (cap-SAY-sin) binds to a nerve receptor called the VR1 receptor, and temporarily changes the shape of the receptor. The VR1 receptor is ordinarily deformed by heat above around 42 oC (108 oF) and its change in shape opens the nerve cell’s gates to charged particles called ions. Ions then flood into the nerve cell, producing a signal to a second nerve. The signal travels from nerve to nerve to reach the brain, and pain, perceived as heat, is felt. You think you’re are hot, but you’re not. You even respond as if you are hot, for example, it makes you sweat. (VR1 stands for “vanilloid receptor 1”. Oddly enough, capsaicin looks like the vanillin in vanilla, except it has a modification that makes it more fat-soluble. Obviously it doesn’t taste like vanilla.)
Capsaicin relieves pain by depleting your nerves’ supply of substance P, the “bad pain” neurotransmitter. Physicians classify pain as “good pain” or “bad pain”. Although you might find it hard to admit that any pain could is “good,” in fact, the short-term (acute) pain that you feel when you accidentally rest your fingers on a hot stove instructs you to jerk your hand away before it is burnt to a crisp, so it is good. “Bad pain” is long-term (chronic) pain, and is mediated by a different neurotransmitter than the one that signals good pain. Nerves that send good pain signals are fast, but nerves that send bad pain signals are slow, and they generate chronic, long-term pain. The bad pain neurotransmitter is called substance P (the “P”, of course, stands for pain). Capsaicin causes your bad pain nerves to deliver off their substance P to other pain nerves up leading to the brain in a big way. The bad pain nerves lose so much substance P all at once that they are depleted of this molecule, and are unable to release any more. Initially pain is felt, but after the substance P supply is dumped, the nerves are no longer able to send a pain signal to the brain, because they are all out of substance P, and don’t have time to make any more.
(Capsaicin binding to VR1 receptors triggers the release of the bad pain transmitter, substance P, initially, but substance P does not bind capsaicin’s VR1 receptors. It binds NK1 receptors, as it travels up to your brain, and new therapeutics blocking NK1 receptors may also prove another method of relieving pain. Incidentally, the dominant neurotransmitter signaling “good pain” is glutamate.)
Whether capsaicin helps depends; are you feeling good pain or bad pain? Bad pain nerves signal slowly, because they are poorly insulated—insulation along segments of nerves in vertebrates allows the signal to jump faster, from gap to gap in between each insulated segment. With less of this signal-accelerating insulation, bad pain signals build slowly but take a long time to die down. These are the same slow signaling nerves that are active in arthritis and other types of chronic, painful conditions, and capsaicin seems useful in dulling this pain.
Fast nerves are more heavily insulated, and conduct good pain, which is felt only briefly. If you burn yourself lightly on a stove and your bad pain nerves don’t kick in to join the slow ones’ complaint, capsaicin may not help your “good” pain get any better.
A new discovery reveals your brains are spicier than you think. You don’t have capsaicin in your brain, but you have similar-looking molecules called endogenous capsaicin analogues. You even have VR1 receptors in your brain for them to bind, but we aren’t exactly sure of all that happens when they do. It seems they are used to signal to you brain that something is wrong in your body, and they enhance your perception of pain. For example, VR1 receptors on the heart were recently discovered, too, and the way you feel a heart attack coming on is your own versions of capsaicin bind to these receptors on your heart. They may have other physiological effects as well, like on blood pressure and respiratory airway constriction.
Capsaicin could point us toward a brand new class of pain relievers. Researchers are currently at work using this information to produce a new class of VR1 receptor blockers as painkillers. Unlike traditional painkillers that work like aspirin or morphine, they could theoretically address pain more directly, and have fewer side effects. One called capsazepine, for example, kept rodents from feeling certain types of pain stimuli. Because these antidepressants resemble capsaicin, they are called “capsaicin analogues.” While it will be exciting to see what drugs researchers can synthesize to relieve our pain in new ways, the red pepper plant has beat them to it.
Good Uses…And Not So Good
It’s nutritious if you can stomach it. The red color of the peppers is from carotene, the same plant pigment molecule that makes carrots orange. Carotene is used by our bodies to make vitamin A, and red peppers are also a surprisingly good source of vitamin C: one small pod red pepper pod contains more vitamin C than a cup of orange juice.
Red pepper can burn you twice. Capsaicin is not chemically altered by your gut, after it is eaten, and any extra capsaicin you do not absorb retains its burning power all the way toward the bitter end. Thus excessive capsaicin can induce a painfully unpleasant bowel movement. Doctors have invented the term “jalapeno-proctitis” for this unpleasant phenomenon.
Here’s how to remove it from your mouth and other painful places. The first step is preventing yourself from having to do this in the first place. Cooks recommend wearing rubber gloves to handle red peppers. If you get it on your skin and it’s too much for you, first try cold, not hot, soapy water. (Heat will deform your VR1 receptors even more, which is what the capsaicin is already doing.) Then, since capsaicin is oil soluble, try fatty, oily things to remove it. This will work if your mouth is burning, too. There are anecdotal reports of using milk, but it might not work so well with skim milk. Buttered bread is another folk remedy, but could work in theory because of the butter. Beer is also supposed to help—if you have your beer cold, anyway, so beer could anesthetize you beyond it’s traditional mode of action.
Substance P makes your nose run. Substance P is more than a pain neurotransmitter. It stimulates inflammatory processes, and if you eat enough red pepper, the consequent substance P dumping inflames your nose a bit, making it run. Some turn this to their advantage if they are congested, and thus it is included in folkloric cold remedies.
For topical pain relief, a prepared product is probably a safer bet than doing it yourself. You can now find these in your standard grocery store. The FDA has approved the use of over-the-counter pain-relieving topical creams containing up to 0.075% capsaicin. Higher concentrations can cause unpleasant burning, making you feel even worse. Although testimonials are never a guarantee of anything, I’ll submit that my own first experimentations with applying these creams very lightly to my sore muscles following weightlifting definitely helped reduce pain to a degree that surprised me. One medical reference(1) tells doctors to advise their patient that they can wash off the cream with watered down vinegar if they dislike the effect.
Watch wear you put it. Since care must be taken not to introduce capsaicin into cuts, wounds, the eyes, or mucous membranes, some preparations come with a ball roller, stick applicator, or patch, to minimize this risk. Some do not, however. Anyone who accidentally transfers a little red pepper under the fingernails to a more delicate area of the body is unlikely to forget the painful result. It’s better if you don’t use your fingers to apply capsaicin creams, anyway, or at least keep track of which finger you’ve used, and watch wear you put it, later. Even after washing your hands thoroughly, a trace left on your fingers can remain for hours and be transferred to your eyeball if you change your contacts lenses. The result is agony.
It could keep your feet warm. Some winter sports enthusiasts sprinkle red pepper powder in their socks, as this reportedly keeps feet toasty; now red pepper powder is being sold commercially for footwarming purposes. My mother, who suffers from poor circulation in her feet, testifies that this works, but also warns our family not to contaminate your underwear drawer with socks that have been used for this purpose.
Interesting Facts There are some fascinating, new, non-medical products being made with capsaicin, as well. For example, capsaicin incorporated inside veterinary sutures can prevent pets from gnawing off their stitches. And a new capsaicin spiked paint is being tested on fiber optic cable, to prevent the cables from being chewed by rodents. The paint has even been used on boats to repel barnacles.
Capsaicin could also keep competition for your birdfeeders by creatures other than birds to a minimum. In a red pepper eating contest, even the most macho, curry-guzzling, salsa-swigging braggart would be knocked out of first place by a bird. Although mammals are affected by capsaicin, birds are not. They have a different type of VR1 receptor. The bird VR1 receptor responds to heat, but is indifferent to capsaicin. Birdwatchers have observed birds nonchalantly dining on red peppers, and later these birds deposit the undigested seeds, facilitating the plant’s distribution. Some inquisitive birdwatcher got the idea to lace their birdseed with capsaicin. This red pepper-birdseed mix is now sold commercially. Birds happily eat the seed, while rodents avoid it. The capsaicin-eating birds reportedly suffer no adverse effects. Indeed, the trace carotenoids and vitamins in the spice is said to give them extra pep.
Evidence of Action Well-designed clinical trials have repeatedly confirmed that topical red pepper creams are indeed quite helpful in treating a number of painful conditions, including rheumatoid arthritis(2), osteoarthritis(3), as well as neuralgias like shingles(4), and diabetic neuropathy(5). It also proved effective treating lower back(6) pain, and in a preliminary pilot study, chronic neck pain(7). It could possibly help those with fibromyalgia, but more study is required to confirm this(8).
A few people in these studies do not tolerate the treatment, and some have especially adverse reactions to it. Others had to apply the cream several times a day for a week until they noticed positive results.
Red pepper apparently generates indigestion in some people, but relieves it in others. For people who suffered ordinary chronic indigestion (without gastrointestinal reflux disease or irritable bowel syndrome), red pepper significantly reduced discomfort(9). On the other hand, another study shows in people who routinely had heartburn, it made their heartburn more painful(10).
There is some controversy over eating red pepper for ulcers. It could theoretically help, and endoscopies proved capsaicin significantly protected people who did not have ulcers from aspirin-generated stomach injury(11). Some have suggested it might help ulcer patients by killing the infecting Helicobacter bacterium frequently associated with the ulcers. Even though red pepper has bacteriocidal activity in the test tube, most herbs do, and you have to be careful extrapolating test tube studies to people. When people with Helicobacter-associated ulcers ate red pepper, it did not have any effect on their infections(12). It may yet still help ulcers by other mechanisms, but more data is needed to render a conclusion.
The Bottom Line
· Red pepper contains capsaicin, which depletes nerves of a pain-signaling molecule called substance P. Red pepper creams applied topically appear successful in relieving certain types of pain.
· Red pepper creams can cause painful burning sensations if applied too liberally, or to sensitive areas like the eyes and mucous membranes.
· Through it’s substance P-depleting mechanism, red pepper may help certain types of indigestion, including ulcers, but make other kinds of indigestion worse, like heartburn. More experimental data is needed to support the effectiveness of this treatment.
· Humans make molecules similar to red pepper’s capsaicin. Blocking their action may lead to the invention of a new class of pain medications.
1 Jellin JM, Gregory PJ, Batz F, Hitchens K, et al. Pharmacist's Letter/Prescriber's Letter Natural Medicines Comprehensive Database. 6th ed. Stockton (CA): Therapeutic Research Faculty; 2004.
2 Deal CL, Schnitzer TJ, Lipstein E, Seibold JR, Stevens RM, Levy MD, Albert D, Renold F.Treatment of arthritis with topical capsaicin: a double-blind trial. Clin Ther. 1991 May-Jun;13(3):383-95.
3 Morris VH, Cruwys SC, Kidd BL. Characterisation of capsaicin-induced mechanical hyperalgesia as a marker for altered nociceptive processing in patients with rheumatoid arthritis. Pain. 1997 Jun;71(2):179-86.
4 Watson CP, Tyler KL, Bickers DR, Millikan LE, Smith S, Coleman E.
A randomized vehicle-controlled trial of topical capsaicin in the treatment of postherpetic neuralgia.Clin Ther. 1993 May-Jun;15(3):510-26.
5 Forst T, Pohlmann T, Kunt T, Goitom K, Schulz G, Lobig M, Engelbach M, Beyer J, Pfutzner A The influence of local capsaicin treatment on small nerve fibre function and neurovascular control in symptomatic diabetic neuropathy. Acta Diabetol. 2002 Apr;39(1):1-6.
6 Keitel W, Frerick H, Kuhn U, Schmidt U, Kuhlmann M, Bredehorst A. Capsicum pain plaster in chronic non-specific low back pain.Arzneimittelforschung. 2001 Nov;51(11):896-903.
7 Mathias BJ, Dillingham TR, Zeigler DN, Chang AS, Belandres PV. Topical capsaicin for chronic neck pain. A pilot study. Am J Phys Med Rehabil. 1995 Jan-Feb;74(1):39-44.
8 McCarty DJ, Csuka M, McCarthy G, et al. Treatment of pain due to fibromyalgia with topical capsaicin: A pilot study. Semin Arth Rhem 1994;23:41–7.
9 Bortolotti M, Coccia G, Grossi G, Miglioli M. The treatment of functional dyspepsia with red pepper. Aliment Pharmacol Ther. 2002 Jun;16(6):1075-82.
10 Rodriguez-Stanley S, Collings KL, Robinson M, Owen W, Miner PB Jr. The effects of capsaicin on reflux, gastric emptying and dyspepsia. Aliment Pharmacol Ther. 2000 Jan;14(1):129-34.
11 Yeoh KG, Kang JY, Yap I, Guan R, Tan CC, Wee A, Teng CH. Chili protects against aspirin-induced gastroduodenal mucosal injury in humans. Dig Dis Sci. 1995 Mar;40(3):580-3.
12 Graham DY, Anderson SY, Lang T. Garlic or jalapeno peppers for treatment of Helicobacter pylori infection. Am J Gastroenterol. 1999 May;94(5):1200-2.