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Are You Crazy to Keep Soap Under the Sheets?

Tucking a bar of soap under the sheets can help prevent leg cramps and possibly even restless legs syndrome (RLS). How does this work?

If you found a bar of soap under the sheets on your bed, you might be startled. Of course, if you’ve been reading The People’s Pharmacy, you’ll know immediately what that soap is doing there. Many people use soap in bed to prevent leg cramps. Others insist that this eases restless legs syndrome (RLS). Here is what readers have told us.

Soap Under the Bottom Sheet Prevents Leg Cramps:

Q. I have been suffering from leg and foot cramps at night for more than a year. This has gradually been getting worse and more frequent, and it was really disturbing my sleep.

About a week ago, I cut up some Ivory soap and scattered it under the bottom sheet. Since I did that, I have not had one cramp. This works!

A. Over the last 15 years we have heard from many readers that placing soap in the bed can reduce the likelihood of leg cramps. There is even some research supporting this concept (see the discussion below). 

Why Put Soap Under the Sheets?

Another reader also found that Ivory soap under the sheet was helpful for both restless legs and leg cramps.

Q. People look at me as if I am crazy when I tell them that I keep a bar of soap under the sheets. I have not had restless leg syndrome nor leg cramps during sleep for more than three years. I use Ivory, since that is what sits next to my bathroom sink.

I tell the skeptics that they are losing out by not trying it. One man, a dentist, still suffers from RLS but refuses to try it.

Soap Against Pain and Cramps:

A. Soap under the bottom sheet may not work for all cases of restless leg syndrome (RLS), but we have heard from many people who find it helpful. Although it has not been studied for RLS, the scent of Ivory soap is effective against the pain of menstrual cramps (Ough et al, Journal of Alternative and Complementary Medicine, July 2008) and fibromyalgia (Ough, Journal of Multidisciplinary Healthcare, Sep. 1, 2008).

Soap and TRP Channels:

We suspect that soap fragrance works by calming hyperexcitable nerves (Behringer et al, European Journal of Applied Physiology, Aug. 2017). We have written about TRP channels and muscle cramps previously. In that case, we were describing how mustard and pickle juice activate TRP channels to release leg cramps quickly.

Various compounds used to scent soap may also trigger transient receptor potential (TRP) channels, especially TRPV1 and TRPA1. Limonene, for example, stimulates TRPA1 (Kaimoto et al, European Journal of Pain, Aug. 2016).

So far, we are only offering this explanation as an hypothesis. We haven’t seen any research to test it. But ever since the beginning of the 21st century, scientists have uncovered increasing roles for TRP channels. In fact, a group of researchers wrote about a father/son duo with an unusual syndrome including restless legs among other symptoms. Both these individuals had a variant genes coding for TRPA1 (Clinical Genetics, Jan. 2018). Of course, this rare variant is not the usual cause of RLS, but the finding does suggest that TRPA1 may be involved.

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies..
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  • Ough YD et al, "Soap-scented skin patch for menstrual cramps: a case series." Journal of Alternative and Complementary Medicine, July 2008. DOI: 10.1089/acm.2007.0819
  • Ough YD, "Soap-scented oil skin patch in the treatment of fibromyalgia: A case series." Journal of Multidisciplinary Healthcare, Sep. 1, 2008.
  • Behringer M et al, "Effects of TRPV1 and TRPA1 activators on the cramp threshold frequency: A randomized, double-blind placebo-controlled trial." European Journal of Applied Physiology, Aug. 2017. DOI: 10.1007/s00421-017-3653-6
  • Kaimoto T et al, "Involvement of transient receptor potential A1 channel in algesic and analgesic actions of the organic compound limonene." European Journal of Pain, Aug. 2016. DOI: 10.1002/ejp.840
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