Suntanned skin may be in vogue today, but for thousands of years it was a thing to be avoided. From ancient Greece right up to about 1900, the wealthy in many northern countries went to great lengths to keep their complexions fair -- tanned skin being a sign of poverty. Tans started to become fashionable when doctors began advocating sunlight therapy around the turn of the last century, but the medical trend was fairly short-lived.
In the late 1700s, a French doctor noticed something unusual: His patients' leg sores healed faster when exposed to the sun. Nothing much came of this finding, though, until a Danish doctor noticed something similar a century later.
Dr. Niels Finsen, who later went on to win a Nobel Prize, noted that his own sluggishness seemed cured with a little dose of sunlight. He eventually showed that solar radiation could help treat smallpox, lupus and tuberculosis. (His work on lupus earned him the coveted prize.)
But sunlight therapy, or heliotherapy as it was sometimes called (helios is the Greek word for sun), didn't become popular until a Swiss doctor, Auguste Rollier, began championing it in the early 1900s.
Inspired by Finsen, Rollier enthusiastically opened solaria -- buildings designed to optimize exposure to the sun's rays -- throughout Switzerland. Soon, the buildings -- all with south-facing balconies, some with sliding walls of windows and retractable roofs -- were mimicked across Europe.
Rollier devised a detailed protocol for how, exactly, to sunbathe for health. He was convinced that early-morning sun was best and that sun exposure was most beneficial when the air was cool. When patients, most of whom had tuberculosis, arrived at his solaria, they first had to adjust to the altitude (his clinics were in the mountains) and then to the cool air. Once acclimated, Rollier slowly exposed them to the sun.
The patients were rolled onto sun-drenched, open-air balconies, wearing loincloths and covered from head to toe with white sheets. On the first day of treatment, just their feet peeked out from under the sheets, and only for five minutes. On day two, the sheets were pulled a little higher, and the patients were left in the sun a few minutes more. By day five, only the patients' heads were covered, their bodies left to soak up sun for more than an hour. After a few weeks, the patients were very tan -- and hopefully very healthy. (The therapy worked for many, but not all.)
Soon doctors across Europe were touting heliotherapy as a cure for tuberculosis and lupus, cuts and scrapes, burns, arthritis, rheumatism and nerve damage. The German military opened sun-hospitals for its soldiers during World War I. Tans became trendy, and many proclaimed sun to be the long-sought fountain of youth.
By this time, scientists had accumulated evidence for the practice too. Researchers showed that sunlight could kill the bacteria that caused tuberculosis and other diseases. Others proved that UV light could cure rickets, a bone disease caused by a deficiency of vitamin D.
But by World War II, the craze for sun gradually had tempered. Newly discovered antibiotics were more powerful against germs than sunlight. And more and more, doctors were seeing proof that too much sun did more harm than good.
That observation, however, wasn't that new. Sir Henry Gauvain, Britain's leading heliotherapist, seemed to foresee heliotherapy's future back in 1922. Sunlight, he wrote, is "like a good champagne. It invigorates and stimulates; indulged in to excess, it intoxicates and poisons."