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.,, July 22, 2012

3. Page, D.H., 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. Kathy

    My RLS was so bad it would even effect my waist on down into my legs! My daughter had been using the soap for a couple of years, she told me she never suffers from restlessness now.
    Well my pain got so bad I broke down and bought a bar of fresh linen scented Dial. It Works! Used it all last week and now if I wake up at night, its not from my RLS!! I’m so glad I found this article, it was making me nuts just wanting to know HOW it works. I’m not so sure its the scent, I can hardly smell it.

  2. Natalie
    Vancouver, Canada

    I’ve been using the soap for about a year, and it works fantastic. I don’t find though that older bars don’t work; I’ve been using the same bar! I have it under the sheet, which wears it a bit I think.

  3. Karen
    North Carolina

    Hello I am 56 yrs old and I have been suffering from leg cramps, thigh cramps. Cramps in my feet and toes for about three years. The cramps are worst after getting steroid injections for arthritis in my knee’s and hip pain. My job also requires me to stand on a concrete floor for ten hrs a day. My cramps come and go all day but a night they are the worst. I have tried eating mustard, drinking vinegar and pickle juice. Well about a month ago my sister in law was telling me about bed soap. I was very skeptical on trying this and to be honest just could not believe this. This year at Christmas she gave me a gift of the Peoples Pharmacy Bed Soap. I came home put a bar under my bottom sheet and went to bed. I woke up the next morning feeling so great and realized that I had not woken one time during the night. I called her and thanked her for the best gift I had ever received. It has been nine days and I have not had a cramp!!! I don’t know how to explain this but I will tell my story to everyone!! Thank you Debbie and the People’s Pharmacy Bed Soap!!!

  4. Daniel
    Adelaide Australia

    I am 36 and have never had a cramp in my life until last week.
    Both thighs cramped up, waking me around 5am. And for what seemed an eternity, I was in the worst pain of my life. 7 years ago, I had a kidney stone and this was much worse.

    Almost in tears, I somehow fell asleep while it was still cramping up. I have dreaded going to sleep every night since. Tonight, I have jumped into bed with a few bars of soap quite excited after reading these posts.I know it will work. So thank you thank you thank you to you all.

    Wish me luck.
    Big hugs from me and the soap

    Am so excited. I just got into bed with my two bars of soap.

  5. Gloria

    I have been an RLS sufferer for years! I do not like taking the medication as sometimes it just does not work. I tried the bar of soap last night. I have not slept that good in years! All I can say is it works!

  6. keith
    Oakland, OR

    It was recommended to me (after I had a very strong, painful “charlie horse”) that I put a bar of soap in the bed near the calf that was causing me great (medium pain) aches as I jogged. I could only jog for about 100 yards after the charlie horse, had to stop and walk, and then jog for a short distance again.

    I used 3 bars of ” lavender” scented soap and the first morning after using it I had almost NO painful calves. After the second night’s use with 6 bars of soap, the calf ache would begin again at about the 100 yard point, but it was much milder and “leveled off”, and I was able to keep jogging for quite a while, enduring a mild ache!

    It works for my calf. Good luck to anyone who uses the soap method. NOTE: I hope more scientists work on this and find some answers.

  7. Tim


    I make soap and a few other similar products for a living. I also suffer from leg cramps at night. So after reading you article and a few others I figured that I would give it a try. I make an all natural product though so no fragrance oils. I thought about adding an essential oil but decided to cut a long thin piece off of an unscented soap loaf I had already made. I put it under my bed and to my delight and surprise the leg cramps ended and never returned (as long as the soap stays in the bed).

    Since I gave a few more to friends and customers who also have leg cramps at night. The results have been immediate and continuous. So good news and bad news on figuring out why this works. I can now say with confidence that it is not related in any way to a fragrance oil added to the soap. It is the soap itself. I will continue to run experiments to see if different types of oils used to make the soap make a difference.

    My working hypothesis is that it has more to do with the soap molecule itself. It is dipolar having a short positive end and a long neutral tail. I am guessing that this would put off a unique magnetic field. Since our nervous system is run with a such a small amount of electricity being transmitted through our nerves it could be influenced by a small magnetic field.

    I would be very interested in any more possible explanations. It would be really great to find a way to test my hypothesis better.

    • Christine
      Pass Christian, MS

      I can’t confirm the science behind your theory, but I use unscented soap for RLS and I find that as long as my leg contacts it, I get relief. In trying to describe what it feels like to others, I explain that my leg feels like it has tiny electrical currents running through it, but when it touches the soap, they are neutralized. The relief is instant for me, and while being skeptical is not protection from placebo effect, I certainly was skeptical until I tried it.

  8. Randy

    Is it not also possible that the scent molecules which diffuse from the soap contact our olfactory gland and lungs and further diffuse into the limbic brain and the brain acts upon the muscles much like aromatherapy or that the scent molecules enter the lungs then partially diffuse across membranes in the lungs and into the blood which then relaxes the muscles as it supplies them oxygen?

  9. terri
    sandusky ohio

    My mom is 82 and uses soap in her bed says it works to take away leg cramps well I try ed it and it works just as she said, instantly takes leg cramp away I just put a bar unwrapped between the bed sheet and the top sheet , can not believe how it works but it does ….wonders

  10. josh

    I am with everyone else who has commented… super skeptical about the idea when I heard about it. But as an RLS sufferer you will try anything. I have had the most restful month of sleep I have had in years. It is strange but the soap releases a cooling feeling of I rest the arch of my foot or the back of my call in it, almost like menthol or aloe vera. It doesn’t matter what brand or if it has a fragrance and the cooling effect lasts all night. So weird but I can’t complain.. it works so well.

  11. Will Willows
    Mid-central somewhere

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

  12. Dds

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

  13. S.g.

    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.

  14. sharon Chisholm

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

    • Joanne

      Where do you put the soap? under the sheets or under the bed pad?

  15. Mercedes L.

    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.

  16. Debbie

    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. :)

  17. JER

    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.

  18. SY

    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.

  19. Joan G.

    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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