by Derek H. Page
There is far too much anecdotal evidence to dispute the fact that soap at the bottom of the bed can relieve nocturnal leg cramps. But contributors to this column have been pleading for a scientific explanation ever since the subject was first raised, nearly twenty years ago. Even after years of discussion there is no consensus on the mechanism. How does the soap ward off the initiation of a cramp? For the leg to be influenced by a signal initiated by the soap, something physical must link from soap to leg.
A crucial clue comes from the work of Professor Ough (1). He found that soap contains a natural scent molecule that has antispasmodic properties. When a transdermal patch was applied using soap as the active ingredient, the severity of menstrual cramps could be diminished. However, Ough does not state precisely how this result can explain why cramps can be alleviated in a leg remote from the active source. How can the scent molecule be transmitted from its place in the bar to the leg muscle?
My colleague and I address this point (2,3). We also suggest that a scent molecule is responsible (whether it be the added fragrance or a natural fragrance). Being volatile, it evaporates from the surface of the bar and deposits on the leg. The molecule is small enough to pass through the skin as in the widely accepted transdermal patch technology. Being vasodilatory, the molecule relaxes the smooth muscles in the leg, increases the local blood supply and thus soothes the cramp. This hypothesis fits all the known evidence. It explains why after some weeks the soap becomes inactive. As the bar ages it dries out and its surface becomes harder and more resistant to the passage of scent molecules. The bar can be rejuvenated by scraping it, thus exposing newer and moister surfaces.
However, the anecdotal record allows for an alternative hypothesis as follows. The active agent, as in the previous hypothesis, is the vasodilating scent molecule. In this hypothesis, however, it is transmitted to the leg by the simple but uncertain process of accidental touch. Soap is soft, and any contact between the soap and the leg is bound to leave some soap behind. In addition soap will be transferred to the sheets which will in turn transfer back to the legs. Movement of the legs in the night may be sufficient to transfer soap to the legs which relieves cramps as described earlier. The anecdotal evidence supports this mechanism. There are cases of successful relief reported in which soaps were rubbed against the calf muscles. Most significantly, the effect of aging of the soap bar, which supported so well the other hypothesis, fits this one also. As the bar of soap ages, its surface becomes firmer and more resistant to transfer by abrasion.
So there we are. We have two hypotheses, neither of which can be disproved by existing data. There is however a very simple experiment that could allow us to determine whether transfer occurs in the vapour phase or only by direct contact. Any reader who has had severe leg cramps and who has been completely cured by placing soap at the foot of the bed can do it.
Use a bed in a spare room that hasn’t been slept in for a couple of weeks and has fresh sheets. Place the soap in a plastic container that prohibits physical contact between the soap and the leg. It must, however, permit easy passage of the scent vapor. Ensure the container is not contaminated on the outside with remnants of soap. Place in the container a couple of bars of soap that you know from experience work. Put the container at the foot of the bed between the sheets and leave it there for at least a few hours to equilibrate. Check that you can smell the scent by putting your head under the covers. Have a shower (without soap!) and get into bed. If you have a cramp in the night you can conclude that vapour phase transfer of the scent molecule is not sufficient to protect the leg from cramps. If you have no cramp the vapor phase transfer mechanism is confirmed.
1.Ough, Y.D., Journal of Alternative and Complementary Medicine, July 2008,14(6) 618
2. Page, D.H. and Smailes, H., Peoplespharmacy.com, July 22, 2012
3. Page, D.H., Peoplespharmacy.com July 26, 2012
This hypothesis was submitted by guest blogger Derek H. Page. We invite you to share your experience below, particularly if you are inspired to carry out his suggested experiment. Should you wish to read some startling “soap stories” here is a link.

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  1. Will Willows
    Mid-central somewhere
    Reply

    It works. I have been using it and no cramps or leg pain for this week. Happy day.

  2. Dds
    Reply

    Ibuprofen is the key! It works wonders on menstrual cramps. I take 3 every 6 hours during painful periods.

  3. S.g.
    Reply

    I don’t know why this works but I DO KNOW that it does! ! I’ve been suffering from bad leg cramps at night for 6 months. I tried the bar soap theory skeptical at first, My leg cramps were gone. I went to stay at granddaughter’s in Arizona, the cramps came back. I had to go to store in morning for a bar of soap never got the cramps again while I was visiting. I am convinced whatever reason being it works.

  4. sharon Chisholm
    Reply

    I used unscented soap and it worked! So it’s not the scent.

  5. Mercedes L.
    Reply

    Just tried this three nights ago. Bear in mind that placebos and “alternate therapies” have never worked on me no matter how much I wanted them to. I have a B.Sci. and am quite the skeptic, but my RLS had gotten so bad of late I would sleep with a giraffe if it gave me relief.
    Three nights in a row, has worked like a charm, including waking up with the start of RLS, thinking “Hhnnn where is my soap?” fishing around for it with me feet, tucking it between my ankles and feeling the RLS just stop dead.

  6. Debbie
    Reply

    I don’t know how to find my original post here, but since that day I posted I’ve had no leg cramps until a few days ago, so replaced my bar of soap in my bed and voila. Guessing it’s been about two months or so, but just letting you know it sure works for a long time, then guess we have to change the bar lol! I was using a full size bar of Zest that was in a wrapper. I purchased a 6 pack of Zest and dang, they were in boxes so I removed the bar I’d been using and replaced it so I’d not have to have a hard box in my bed. :)

  7. JER
    Reply

    I have had 90 hours of training in aromatherapy at an accredited community college. Here is a suggestion for the mechanism of the soap effect. The olfactory nerve is the only nerve in the body which has a direct connection to the brain. It is so sensitive, and unfortunately, most of us are not even aware of the effects that volatile molecules have on our bodies via that nerve. There is plenty of literature that discusses this mechanism.

  8. SY
    Reply

    I had severe leg cramps since childhood. I am now in my 80’s and only recently in a chance conversation with a Canadian friend was told about the soap treatment. I could not believe how immediate the relief was that very night. I have been telling groups and individuals about it since. Incidentally, it must be the vapor theory since I do not unwrap the bar of soap.

  9. Joan G.
    Reply

    I am an elderly woman who has had leg cramps for years. Not much help, chemicals don’t help. A friend told me of soap in your bed and no more night cramps. Such a relief–it works. I’ve told many friends, and their results are very positive..

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