Today, America’s increasing obsession with health and wellness may be contributing to the rise of clothing-optional vacations. “Americans have moralized healthy bodies,” said Dacher Keltner, a professor of psychology at the University of California at Berkeley, who has studied moral emotion and judgment. He added that “a case could be made that people are traveling to these places to be pure for moral reasons  to achieve harmony in nature.” It’s really a form of self-expression, he added, that dates back to Walt Whitman and John Muir, as well as Thoreau, all of whom advocated being as true to yourself as possible. “The truest you can be is taking off those clothes,” he said.

Suzann Zane, a 26-year-old bartender from Baltimore, decided to try her first nude vacation this year  a weekend getaway in January to the Avalon Resort in Paw Paw, W. Va.  partly because of her interest in getting back to nature. “I consider myself a minimalist,” said Ms. Zane. “With this big societal push for becoming green, we need to kind of get back to our roots and I thought maybe this would be a good way.” The first clue that this would be a different kind of vacation came on the drive up the long winding road to Avalon. The first sign Ms. Zane said she spotted was one that posted the speed limit at 7 m.p.h. The second announced, “Beyond this point you will encounter nudity.”

When Susan Sullivan, 42, from New Jersey, visited her first nudist resort last year with her boyfriend, John Sheilds, 55, she said she had to warm up to the idea of disrobing in front of strangers by draping a towel over her body when she first went outdoors. But after a short while, she too lost any inhibitions. “You come to the realization you’re looking at those people, you’re not staring at people. They’re not staring at you.”

SpaFinder’s chief executive, Pete Ellis, theorizes that the increase of spas at resorts has influenced the growing acceptance of nudity. After all, disrobing for a massage has become a routine vacation ritual for many travelers. Even the staid Canyon Ranch Resort in Tucson, Ariz., has nude sunbathing decks off both the women’s and men’s locker rooms with an unlimited supply of sunscreen.

Warm-weather resorts from Palm Springs to Miami Beach to the Caribbean say they are seeing (and turning a blind eye to) more topless sunbathing at their pools and beaches as the strength of the euro brings more Europeans, and their more relaxed attitude toward nudity, on vacations to this country.

So many European guests were sunbathing topless on the beach at Starfish Trelawny, an all-inclusive family resort in Jamaica, that the resort put up a bamboo fence at the eastern end of its beach a few years ago to keep conservative guests happy and teenage boys from gawking. And Shan Kanagasingham, the general manager at The Tides, in South Beach, recalls her first stay at the hotel when she got the job about a year ago. “When I checked in for the first time to the Tides  and I’m not making this up  I opened the window and looked out, and all I saw was this sea of breasts and people walking around in G-strings.”

The spa at the Parker Palms Springs, which opened about two years ago, offers separate men’s and women’s areas each with pools and relaxation areas, all of which can be used in the nude. “And trust me, they are,” said Marisa Zafran, the hotel’s spokeswoman.