www.nytimes.com – Two young women in white chamois robes exited the Himalayan salt sauna at Premier57, a spa in Midtown Manhattan, looking rosy and happily spent.

The salt sauna, lined with burnt orange and yellow blocks of sodium chloride, is a popular destination at the spa, where a day pass is $75 and the tagline urges guests to “immerse, indulge, intrigue.”

Options include an infrared lounge, a meditation room, an igloo room, a gold sauna and a clay sauna, “but we have a lot of guests who just come here for the salt room, especially if they have arthritis,” said the spa’s general manager, Ellis Kim. “It’s very good for arthritis and for regulating blood pressure.”

There’s no scientific proof for such claims. And, despite the assertions by Ms. Kim and her peers, there is also no proof of the power of salt rooms to bring relief to children with asthma, seniors with chronic obstructive pulmonary disease and everyone in between with stuffy noses or stress, according to Dr. Norman H. Edelman, a senior science adviser at the American Lung Association.

Nonetheless, salt therapy, also known as halotherapy, a venerable treatment in Central Europe and Asia, is now being offered at spas, resorts and stand-alone facilities in the United States in the form of salt beds, salt rooms and salt booths. Floors and walls that are lined with salt blocks and salt crystals, and zero-gravity chairs (recliners designed to relax the back), are the norm. A device known as a halogenerator grinds sodium chloride into a dry aerosol, then disperses it to mimic the microclimate of a salt cave.

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