Sauna Industry Is Hot, Hot Part of $2 Trillion Wellness Market

The bathhouse tiles echo with splashing water and hissing steam as you step down to the cold-plunge pool. On the final stair, the 29-year-old analyst in front of you starts to turn back, muttering something about forgetting his towel. “Coward,” you think.

In the sauna your body had been crying out for relief from the heat, but plunging into the water feels like being stabbed by a thousand tiny knives. You try to focus on breathing, but your body, betrayed, considers that out of the question. To the people shuffling past from sauna to showers to cold plunge, you look ...