For generations, some people have kept an ordinary bar of soap near their bed—or even rubbed it lightly across their sheets before going to sleep. It sounds like an old-fashioned cleaning trick, but the reason usually has little to do with washing the bedding. Instead, the practice is often connected to a traditional home remedy for nighttime leg discomfort.

The idea is most commonly associated with leg cramps and restless legs. Some people place an unwrapped bar of soap underneath the fitted sheet near their legs, while others rub dry soap over the sheets themselves. They swear that doing so helps them relax and reduces the uncomfortable sensations that can disturb their sleep.

There are several theories about why people believe it works. Some explanations focus on the fragrance or ingredients found in certain soaps, while others suggest that the ritual itself may create a comforting association with bedtime. However, there is no strong scientific evidence showing that a bar of soap under the sheets can reliably prevent restless legs syndrome or nighttime muscle cramps.

There is another practical reason some people lightly rub pleasantly scented soap over bedding: fragrance. A dry bar can leave a subtle clean smell on fabric, similar to placing scented soap inside drawers or closets. That can make freshly made bedding smell pleasant without actually washing it again.

So if you’ve seen someone doing this, the answer is usually surprisingly simple: they’re following an old home remedy believed to help with nighttime leg cramps or restless legs, or they’re using the soap to give their bedding a fresh scent. It may be a tradition people swear by, but it shouldn’t be confused with a medically proven treatment.