Thursday, November 24, 2016

Bar soap and leg cramps

[While spending Thanksgiving with the family, someone reported with some diffidence sleeping with a bar of soap, which had dramatically resolved excruciating nocturnal leg cramps.  I then discovered quite a literature on this subject.]

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…

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…

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…

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.

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.

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…

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…

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. 


  1. [Snopes rates as "unproven".]

    While all of the above have been said to avert the problem in at least some cases, one further suppression trick appears to work, at least according to anecdotal information, for almost everyone so bedeviled: sleeping with a bar of soap in the bed. No one has yet produced a plausible explanation as to why snoozing with one's Ivory might stave off those devastating nocturnal leg cramps, yet the reports of its doing so are numerous.

    Slipping a bar of soap into the bed as a leg cramp prevention has been advanced by a number of authorities, both medical and otherwise. Ann Landers has mentioned the soap cure in her column on a number of occasions, with each airing prompting a load of letters from readers thanking her for this information because it worked wonders for them. "They were thrilled and grateful to be liberated from those leg cramps," said Ms. Landers.

    As to how this works — or even if it does — we're still in the dark. Perhaps soap releases something into the air that is beneficial to those predisposed to this condition, with the bedsheets working to contain the helpful emissions to the area where they are needed. Or perhaps this is a case of believing making it so — the soap itself has no effect, but the sufferer's faith in the procedure serves to effect the miracle.

    Yet skepticism aside, for those subject to nocturnal leg cramps, this bit of folk wisdom is clearly worth a try, in that the only potential downside is their having to share their beds with slivers of soap. (Well, that and having their spouses think them a bit loony.) As to what sort of product and where to place it in the bed, although some who pass along this bit of housewifely lore indicate specifics such as the soap's having to be unwrapped or not be a specific brand (Dial and Dove are often mentioned as bars to eschew), those who swear by the procedure have had success whether they used large bars or the small ones commonly found in hotel rooms, whether the cakes of soap were wrapped or unwrapped, and whether the afflicted leg was rested on top of the soap or not. As for which brand is best, cautions against Dove and Dial to the contrary, they all seem to work about the same.

  2. However, there is one simple thing you can do TONIGHT that will stop restless leg syndrome and leg cramps.

    Put a bar of soap under your sheet!

    That’s right. About 42% of people who suffer from leg cramps or restless leg syndrome use this weird soap trick to stop the problem. Why does it work? Doctors are not sure, but some believe that the magnesium in the soap stops the problem. That is because magnesium deficiency is a leading cause of both restless leg syndrome and leg cramps.

    Dr. Oz suggests lavender soap because it helps to relax the muscles with its natural scent. I agree. If you are going to put soap in your bed, make it natural with an essential oil-based scent.

  3. Virginia news station WSLS 10 recently ran a 'myth buster' segment on whether putting a bar of soap between your sheets can ease nighttime leg and foot cramps. To my surprise, they concluded that, yes, a bar of soap does seem to help some people, even though there is "no scientific evidence" for why this would work.

    Just to clarify, the claim is that merely having a bar of soap near your muscles at night can stop them from cramping. The brand of soap doesn't seem to matter much, though some people express individual preferences. (Irish Spring is a favorite.) The soap should also be in close proximity to the cramping muscle. Some people say that if cramping starts, they simply adjust their position so that the soap is making contact with the muscle, and the cramping and pain stops.

    To say that there's "no scientific evidence" for this claim seems like an understatement. The idea sounds totally absurd. However, a quick google search reveals a large number of people who, despite initial skepticism, now swear by the method. Even Snopes lists the claim as 'undetermined'. So what could be going on here? Could soap actually have muscle-calming properties?

    The most obvious theory is that the cramp relief is simply a placebo effect. People believe that it'll work, so it does. But it seems premature to dismiss the phenomenon in this way. Perhaps there is some strange bio-chemical effect at work.

    Unfortunately, there's been very little scientific investigation of the soap phenomenon. The one relevant study I could find was published in the Journal of Alternative and Complementary Medicine. Dr. Yon Doo Ough (of Beloit Memorial Hospital in Wisconsin) and colleagues investigated whether soap-scented skin patches could ease menstrual cramps. Their study was directly inspired by soap's use in preventing nocturnal leg cramps. They theorized that it was the smell of the soap, not the soap itself, that was having the antispasmodic effect. So they applied soap-scented oil to skin patches and tested them on women with a history of severe menstrual cramps. The women reported that the patches did help.

    So until a better theory comes along, I'm willing to accept the possibility that soap between the sheets might ease cramps — perhaps because the smell somehow tricks the brain into ignoring the pain and suppressing the cramping response. Though the mystery is why applying the soap directly to the muscle seems to help. Would it be equally efficacious to put the soap directly to your nose?

    As the WSLS myth-buster segment pointed out, the technique is cheap and harmless. So if you suffer from nocturnal leg cramps, I guess it's worth a try. There's nothing to lose.

  4. I have used your handy hint on putting soap in the bed for nighttime aches and pains. I’ve also shared it zealously here in Western Australia for more than a decade.

    I hereby stand on my soapbox to tell the world that it works 95 percent of the time! I don’t feel it is a placebo effect because one of my converts says that her arthritic dog, who always slept on her bed and struggled to the floor each morning, literally bounded off after the second night of being “soaped.” You can’t tell me that the dog knew why there was a lump in the bed!

    I could fill a book with success stories, but I just want everyone who has ever had a niggling ache to give it a go. It costs nothing, and if it falls out of the bed, then consider bending down to retrieve it as the start of your morning exercises. Why can you bend down? Because the soap worked.

  5. From a colleague: It's all in the "unknown molecule"!