Are You Crazy to Keep Soap Under the Sheets?

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.