Many years ago we received a message from a reader of our syndicated newspaper column about putting soap under the bottom sheet to prevent nighttime leg cramps:
“Under the cover of darkness (so my husband, who is an M.D., wouldn’t see), I slipped a bar of soap under the sheet on my side of the bed. For two nights I continued to have mild leg cramps but by the third night they were gone. I have not had them since.”
Since that early letter we have received hundreds of messages from people all around the world regarding the soap treatment for muscle cramps. Many doctors (and quite a few non-health professionals) are absolutely convinced this is total nonsense. They chalk it up to a placebo effect, largely because they cannot imagine how it could possibly work.
Two thoughtful and curious readers came up with a hypothesis. They submitted the following explanation for the benefit of the skeptics:
The following hypothesis was contributed by Derek H. Page and Hugh Smailes:
Several years ago, the advice columnist Ann Landers raised a provocative question in her column: does soap at the foot of the bed cure night-time leg cramps? The consensus in the medical community is no: there is no conceivable mechanism by which it could, so any relief derived from this procedure must be due to the placebo effect. In other words, it’s all in the mind.
But if it is indeed a placebo effect, it’s a remarkably strong one. Many people who have suffered for months, if not years, from painful, nocturnal cramps in their legs and feet have found immediate and long-lasting relief just by slipping a thin, innocent bar of soap beneath the sheets. Some even report relief although they were unaware that a bar of soap had been snuck into bed.
Likewise, others whose cramps have mysteriously returned have been nonplussed until they later discover that their bars of soap have fallen from the bed. From the point of view of those who, like us, are trying to solve this mystery, it is fortunate that several websites (including this one) have maintained reports of this unusual treatment and its results.
A Potential Explanation:
We decided that although these data were anecdotal, and therefore suspect, we would treat them as if they were scientifically valid, and use them to try to develop an explanation for soap’s seemingly helpful effects. But as soon as we started reading the literature, we realized what an enormous task we had undertaken. The anecdotal literature is vast, and frustratingly contradictory.
Nevertheless, we decided to continue, recognizing that any explanation we produced would remain an untested hypothesis. It would require testing by others before it could be elevated to the status of a theory. We decided to condense the relevant literature down to a few points on which there is general agreement. Here are the main relevant observations taken from the anecdotal evidence:
What People Report:
- It seems to work for many people. Soap in the bed appears to alleviate nocturnal leg cramps.
- Relief is immediate and sustained.
- Some people report that soap does not work. It appears either to work consistently and well or not at all. There are few cases of partial success.
- After a few months, a bar of soap is no longer effective for preventing cramps. It must be replaced. Old soap can be rejuvenated by scoring or shaving it to produce fresh surfaces.
- Some subjects have placed the soap between the sheets, and some have placed it under the bottom sheet. Either or both of these methods work.
- Some subjects report that direct physical contact between the subject and the soap is desirable, but few claim it is essential.
From these observations, certain conclusions may be drawn. For our purposes, number 4 on the above list is the most relevant. Apparently, the phenomenon can be switched off and on: off when the soap bar ages, and on again by scoring the soap. But why? What is it that’s being switched off and on?
We hypothesize that it is an as-yet-unidentified molecule present in the soap. This might sound like a stretch, but in fact, this “switching” mechanism is consistent with what we know about the structure of soap.
Soap is a water-swollen gel. When it’s purchased, its moisture content is generally somewhere between 5 to 15 percent. Soap is very porous, and when it’s swollen with water, it permits small, dispersed molecules to pass through it. But when it has aged, its surface dries out, and its surface is a lot less porous, so small molecules can no longer pass through it.
Refreshing the Soap:
We think that an unknown molecule that diffuses out of the soap gel is responsible for alleviating cramps. As long as the bar is emitting this molecule, the cramps are suppressed. An old bar of soap ceases to emit the molecule as the surface dries out and its resistance to diffusion rises. That’s when the cramps return. The bar can emit again–and once again eliminate cramps–after new, moister, fresher surfaces are exposed by scraping the bar of soap.
From items number 5 and 6 from our list above, we know that direct contact between soap and skin can be helpful, but it does not seem to be essential. This suggests that our unknown molecule is volatile, capable of diffusing in air: i.e., that it can pass from a bar of soap to your cramping leg in a manner similar to the way a drug is transmitted through a skin patch.
Soap Scented Oil (Fragrance): The Magic Molecules?
After generating this hypothesis, we took a careful look at the list of ingredients on a package of soap, and we found only one possible source of small molecules of a volatile compound: the fragrance. Nearly all soaps contain fragrances or perfumes. Certainly those mentioned in the anecdotal evidence do. And what perfumes are used in soaps? That’s generally top-secret information, held close to the vest by soap manufacturers. But we do know that most soaps contain esters and oils, such as carrot oil and lavender oil (or their synthetic doppelgangers). These compounds are vasodilators. Like the ester nitroglycerin, which is used to alleviate pain caused by angina, they enlarge blood vessels.
The quantity of perfume transmitted to the skin may be small, but it appears to be enough to dilate blood vessels and prevent cramps. We know, of course, that the small, mobile molecules in the fragrances of soap diffuse through its gel to the surface and evaporate. We know because we can smell them. And when you score an old bar of soap, you can smell it all over again, just as strongly as when you first took it from its paper wrapper.
Who Will Test the Hypothesis?
Before it can be accepted, every new hypothesis has to be tested. We would welcome the findings of anyone who might want to test our hypothesis, and we would be eager to see the results. To the research community, which is convinced that ion imbalance is responsible for the initiation of cramps, we say that this suggestion doesn’t challenge that. There is ample room here for research by the academic and medical communities. Our proposed mechanism will surely be under attack within the week. Yet it fits much of the data so well that we suspect that whatever future research results are obtained the final conclusion in this matter will include much of what is written here.
Soap for Other Pain Problems?
Finally, it has not escaped our notice that if this explanation is correct, it may have applications beyond the alleviation of leg cramps–specifically, but not only, in the management of pain from other conditions. We hope that having proposed this scientifically viable explanation for the phenomenon of soap alleviating leg cramps will validate the experiences of those that have benefitted from this “treatment,” and open this area of inquiry to further medical and academic research. We do not claim originality for every element of this proposal. But we do claim originality for putting together the pieces of this puzzle.
To those who have been unable to get relief with the soap treatment (i.e., those mentioned in item 3 above), we suggest you persevere and try a different soap with a stronger scent, potentially scoring it. You might try searching the internet, or this website, to see if there’s a brand others have had good luck with. The fresh, unwrapped bar of soap should then be placed between the sheets, preferably in a location where the soles of your feet can touch it. And please report back to us whether or not it works–we’d be very interested to hear.
Dr. Derek H. Page, (Baie D’Urfe, Quebec, Canada) and Hugh Smailes (Apollo Bay, Victoria, Australia) As a final disclaimer: we are not physicians and have no health expertise, as our critics will doubtless be happy to affirm.
An Update on Derek and Hugh’s Hypothesis:
Several years ago an anesthesiologist by the name of Dr. Ough actually did some research on soap to relieve cramps. At that time he was working at Beloit Memorial Hospital in Beloit, Wisconsin. He reported his findings in the Journal of Multidisciplinary Healthcare (Sept. 2, 2008):
“…I assembled a skin patch made of crushed bar soap, and achieved successful results in regards to relief of muscle cramping and pain. I further experimented with the use of this soap patch for various other painful medical conditions.
“It was noted that the soap patch was successful in relieving pain from muscle cramps, knots, and even the trigger point pain associated with chronic myofascial pain syndrome. The soap patch also is effective for smooth muscle spasms, relieving the pain from menstrual cramps, intestinal cramps, and kidney stone.
“Hypothesizing that the scent of the soap was the active ingredient responsible for alleviating pain, I have since assembled the skin patches with a soap-scented oil (SSO), rather than bar soap itself, and hope to continue to expand its applications to other disease states…
“…I hypothesize that the active ingredient in the SSO skin patch is the scent itself. This would represent a new and unique method of medicinal delivery, because the scent is seemingly absorbed through the skin and not via the olfactory system.
“From these results, I conclude that the SSO skin patch is a safe and effective topical treatment for the pain of fibromyalgia.”
Joe’s Alternate Explanation for the Soap “Cure”
The world changed for us when we learned about research carried out by a Harvard neurobiologist, Bruce Bean, PhD and his buddy Rod McKinnon, MD (a Nobel prize winner). They concluded that muscle cramps are caused by overstimulation of nerves rather than by dehydration or electrolyte depletion. They heard about the old wives’ tale that eating a spoonful of yellow mustard or drinking an ounce of pickle juice could interrupt muscle cramps within minutes.
After years of experimentation they were able to explain this phenomena through nerve stimulation of the mouth, throat and stomach. TRP receptors in those organs were affected by strong flavors (cinnamon, ginger, hot pepper extract). Within minutes, stimulation of those sensory nerves could interrupt muscle cramps in legs. Details of their research efforts can be found at this link.
Soap Stimulating Nerves:
Now that we know muscle cramps are triggered by overactive nerves and can be calmed by stimulating sensory neurons in the mouth, esophagus and stomach working through the spinal cord, we think we have an explanation for the soap “cure.” The soap scented oil that is the basis for the fragrance that Derek and Hugh write about above could also be stimulating sensory nerves in the legs.
It turns out that there are both olfactory (smell) and taste receptors in the skin. We are normally not aware of them, but they exist. It is entirely possible that fragrance in soap creates a low-level of sensory stimulation that goes through the spinal column and calms the nerves causing muscle cramps. Because it is a much slower process than swallowing strong flavors (like mustard or vinegar), it can take a day or two for the effect to manifest itself. We think that the most active ingredient is limonene, a volatile fragrance derived from the rinds of limes, lemons and oranges.
Soap for Hand Cramps:
Many people have told us that when they get hand cramps they can interrupt them quickly by holding a bar of soap. Here is a link that describes this exact scenario.
We recognize that this is all a hypothesis rather than proof positive. But we think that nerve stimulation represents a plausible explanation and enhances the theory that Derek and Hugh offer at the top of this article.
What do you think? Have you experienced quick cramp relief from mustard, pickle juice or tonic water (another strong flavor that likely stimulates nerves)? Has the soap trick worked to prevent leg cramps. Share your experience below in the comment section and let us know what you think of our revised theory. At the time of this revision there are over 300 comments. Why not take a moment to read some of them and add your own.
Revised: by Joe Graedon, 10/20/16