What Is Epsom Salt and Should You Be Bathing In It?

May 2, 2017 1:57 PM EDT

Epsom salt was first discovered in the 17th century in England, and for hundreds of years it’s been dissolved into baths to ease aches and pains. In other words, it’s nothing new. But over the past couple of years, Epsom salt baths have enjoyed a resurgence, with high-end spas offering float sessions inside sensory deprivation tanks and celebs like Gwyneth Paltrow and Hannah Bronfman revealing they swear by their therapeutic effects.

What is Epsom salt?

First of all, it’s not the stuff you sprinkle on your food, and it’s also not the same thing as bath crystals. Epsom salt is crystallized magnesium sulfate, and you can buy a bag for a few bucks at most drugstores and on Amazon. But although the home remedy has been around for generations, there isn’t much proof it actually works. “When you really look at the research and the studies that are out there, there isn’t anything overwhelming saying that it’s really effective,” says Dr. Bret C. Jacobs,  clinical assistant professor  of orthopedic surgery and sports medicine at  NYU Langone Medical Center. “But at the same time, there’s also nothing to really refute it.”

What does Epsom salt do?

The theory is that magnesium in these salts is absorbed through the skin, in turn relieving inflammation throughout the body. According to Jacobs, some research has shown that soaking in an Epsom bath led to some fluctuation in magnesium levels in blood and urine samples. But, for the most part, your skin is a waterproof barrier, and won’t absorb all that much magnesium, Dr. Jacobs explains, and skeptics attribute the positive effects of these baths to the warm, soothing water, or the placebo effect. “It’s been used for years and years, since 1650—so in a way, you can’t go against 350 years of anecdotal use,” he says. “If it were extremely harmful, we’d probably hear more bad stuff about it.”

What are the benefits of Epsom salt baths?

Aside from soothing aches and pains, people take Epsom salt baths for a variety of reasons. None are backed by research, so take this advice with a grain of, well, salt:

Relieve stress: Magnesium levels drop when you get stressed out, so some believe soaking in a bath of magnesium-rich Epsom salts may promote relaxation, good mood, sleep, and overall wellness.

Ease bloating and constipation: Magnesium and sulfate allegedly draw excess fluid out of your system, flattening your tummy. “At this point, the only thing we truly know about Epsom salts is if you take them orally, they can regulate your bowels,” says Jacobs. “That’s actually the only FDA approved use for it.” But this natural laxative could result in other complications—so just like with any new medication—be sure to speak with your doctor before giving it a try.

Treat migraines: Magnesium deficiency has been linked to migraines.

Soothe tired feet

Exfoliate skin

Treat ingrown toenails

Relieve joint pain

How to prep an Epsom salt bath

The Epsom Salt Council recommends dissolving 2 cups of Epsom salt in 15 gallons of water (the amount in a standard-sized tub) and soaking for 12 minutes.

This article originally appeared on Health.com