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 one reader told us.

Why Put Soap Under the Sheets?

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, so we anticipate that at some point investigators will discover how they affect RLS.


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