A bar of soap usually belongs beside the sink or in the shower, but some people have been placing one under their bedsheets for generations. The unusual bedtime trick is especially associated with people who experience nighttime leg discomfort or occasional leg cramps. Instead of reaching for a complicated remedy, they simply rub a dry bar of soap across the sheet or tuck it near their feet before falling asleep.

The tradition has been passed through families for years, with supporters claiming that the soap somehow makes their legs feel calmer at night. Lavender and other lightly scented varieties are particularly popular because their fragrances are often associated with relaxation. Yet there is a surprising problem with the story behind this household trick: despite countless personal reports, researchers have not established strong evidence that soap itself prevents nighttime cramps. So why do people continue doing it, and what might actually explain the strange ritual?