Jessica Biel Soaked in 20 Lbs. of Epsom Salt Before Met Gala — What Are the Benefits?

Jessica Biel shared the headline-making way she got ready for the Met Gala on May 6 — but her pre-gala soak in Epsom salt left some fans wondering why.

“I know some people like to party before Met Ball and party all weekend, and all the things and I have total respect for that. This is what I do to get ready for Met Ball,” Biel, wearing a plush robe embroidered with her name, began her TikTok video.

 The actress showed a row of five, 4-lb. bags of  Dr. Teal’s Epsom Salt lining her bathtub.

“Twenty pounds of Epsom salt in a bath. Here we go for real,” Biel, 42, said, dumping the bags in the water. “Water as hot as you can take it, 30 minutes soak,” Biel explained. 

“Tons of water, then off to bed early.”

The brand of Epsom salt she used, Dr. Teal's, commented, “About to be the most relaxed star at the Gala 🛁⭐️,” prompting Biel to reply, “You know it.”

The company suggests using 2 cups of the salt in a bath and soaking for 20 minutes. It “soothes the body and provides the ideal opportunity to relax in a warm bath, quiet the mind, de-stress and revitalize skin," Dr. Teal's says.

Epsom salt gets its name from the English town where the salts were first discovered in the seventeenth century, according to the National Library of Medicine, which says that "high society flocked to take the medicinal waters." The high magnesium content was thought to encourage relaxation.

But these days, you don't need to travel to a countryside spa town: “The idea is that when you pour Epsom salt into warm water, it dissolves the magnesium and sulfate and allows it to be absorbed into your body through your skin,” the Cleveland Clinic says. 

And although “there are no definitive studies showing that magnesium can be absorbed through your skin in sufficient amounts to address potential deficiencies of the mineral,” Epsom salt baths are commonly recommended “to people with muscle pain and mental stress.”

In fact, magnesium is often used as a sleep aid and was recently the main ingredient in the “Sleepy Girl Mocktail,” a TikTok beverage recipe that claimed to help people get better rest.

“There are studies that show that people that struggle with anxiety or even depression tend to have lower levels of magnesium and when supplemented, the anxiety does improve,” Kristina Freshour, a registered dietician at the Katz Institute for Women's Health, told PEOPLE.

However, it's important to note that the magnesium in the mocktail and other supplements is designed to be taken orally; The Cleveland Clinic says ingesting Epsom said "can cause serious side effects such as severe diarrhea."

And there can be risks to the baths, Dr. Laura Purdy, a family medicine physician and medical director of Swell Medical, told Yahoo Life. 

“There may be some skin reactions if you have sensitive skin, like a rash or itchy skin,” she said.

Others told the outlet that using very hot water, as Biel recommended, can lead to dehydration — but Biel did say to drink "tons of water."

As the Cleveland Clinic recommends, “If you’re curious about Epsom salt baths or have any concerns, check with your healthcare provider before using Epsom salts.”