Naked? With strangers? In Europe it’s how you relax at the spa.

In countries like the United States, he said, there is a “highly sexualized and puritanical culture, where sex is tightly controlled. Attitudes tend to be much more conservative when it comes to what women do and women’s bodies. In Europe this is generally less the case.”

In a number of studies, Dr. West and his team did just that found it that being naked around others can increase self-confidence and life satisfaction. “When you go to a naturist event, you see a lot of normal people, people who don’t have an airbrush and aren’t Beyoncé, and you realize that you don’t look bad compared to the average person,” said Dr. West. “And you spend time naked in their company and nothing bad happens. No one says anything bad to you, no one laughs at you.”

Some Americans have discovered that the discomfort of being naked in the sauna is temporary and worth it.

After moving to Graz, Austria, Amy Feineman, 38, a saddle fitter originally from Colorado, made the hour-long drive to Rogner Bad Blumaua colorful, trippy thermal bath and hotel designed by Friedensreich Hundertwasser, an Austrian architect believed that “the straight line is the bane of our civilization.” At the thermal spa (day visit, €57), this philosophy translates into undulating floors, round buildings with uneven ceilings and bright orange, blue and green mosaics. On their first visit, Mrs. Feineman and her husband skipped the nude sauna, instead exploring the pools and outdoor gardens partially clothed. But on their second visit, they felt brave enough to bare everything in the sauna.

“It took us most of our first day there to build up the courage to go see it, and then we spent most of our time there,” Ms. Feineman said. “I’m a plus-size person and in the US I would never wear a bikini in public. Here I am happily walking around in the nude area.”