For many years now, readers have been telling us that putting a bar of soap under the bottom sheet of the bed can help reduce leg cramps. Others report that soap between the fitted sheet and the mattress pad can help relieve restless leg syndrome. Occasionally, we hear from a person who has found that soap alleviates arthritis pain. One reader just wrote that this odd remedy helped ease foot pain due to tarsal tunnel syndrome.
Soap Under the Bottom Sheet for Foot and Ankle Pain:
Q. I have been diagnosed with degenerative joint disease and also have tarsal tunnel syndrome in my left leg and foot. The pain is truly unbearable.
When I read in your column about people who put soap under the bottom sheet of the bed, I decided to try it. After a month, I now have much less pain and more energy.
Tarsal Tunnel Syndrome:
A. In tarsal tunnel syndrome, the tibial nerve running into the foot through the ankle gets compressed. That causes significant discomfort, similar to carpal tunnel syndrome in the wrist. Symptoms include pins and needle sensations, shooting pains, electric shock sensations in the foot or a burning feeling.
We can’t explain why soap might help, but we were delighted to hear that something so simple could be beneficial. Doctors often treat this uncommon condition with NSAIDs, steroid injections or, in extreme cases, surgery. However, scientists have not conducted adequate rigorous research to guide treatment (Neurological Sciences, Oct. 2017).
We suspect that some of the effects of soap under the bottom sheet are due to activation of TRP (transient receptor potential) channels in the nerves. These channels, especially TRPV1 (which reacts to heat and to capsaicin, among other substances), TRPA1 and TRPM8 (which reacts to cold and to menthol), are important mediators of neuropathic pain (Current Opinion in Pharmacology, Feb. 2017). Tarsal tunnel syndrome is a type of neuropathic pain, so perhaps that is why the soap has been helpful.