Light and Human Health #1 – When Light Was Medicine: A Forgotten History

Ancient Beginnings: Hippocrates and the “Sunny Side of the Hill”

In ancient Greece and Rome, sunlight was considered one of the pillars of a healthy life. Hippocrates, the Father of Medicine, described the influence of sunlight and environmental exposure on health in his treatise On Airs, Waters, Places. He observed that people living in well-sunlit regions were generally healthier and recovered more quickly from illness.

Hippocrates noted that those who lived on “the sunnier side” enjoyed better health and regained their strength sooner — one of the earliest recorded observations linking light to human well-being.
(Source: Hippocrates, Airs, Waters, Places, ca. 400 BCE)

Temples of healing, bathhouses, and gymnasia were designed to capture as much natural light as possible. Heliotherapy was a routine, everyday practice.

The 19th Century: Florence Nightingale and the Light That Heals

With the rise of the Industrial Revolution, people began to lose regular access to daylight. Factories, narrow streets, dim apartments, and long working hours indoors contributed to widespread illness. It was in this context that Florence Nightingale, the founder of modern nursing, made an observation that would reshape medical care. She noticed that patients placed in bright, airy rooms recovered more quickly. In her most influential work, she wrote:

“Second only to their need of fresh air is their need of light… And it is not only light but direct sun-light they want.” (Source: Florence Nightingale, Notes on Nursing, 1860)

Light became a principle of medical architecture – windows were enlarged, wards were oriented toward the east, and beds were moved closer to the sunlight.

Swiss Sanatoria: Patients on Mountain Slopes in Sunlit Beds

At the turn of the 19th and 20th centuries, Switzerland became the centre of a heliotherapy revolution. Physicians such as Oskar Bernhard and Auguste Rollier believed that sunlight, applied in carefully measured doses, could support the treatment of conditions that conventional medicine could not effectively address, including bone tuberculosis.

Rollier established a network of “sun clinics” in Leysin. Patients lay in beds arranged on terraces and mountain slopes, regardless of the season. In winter, they were wrapped in blankets, but their faces and bodies were gradually exposed to the light.

The results were promising enough that Swiss sanatoria gained international recognition. Photographs of patients “sunbathing in beds on snowy slopes” remain some of the most striking images of this era.

Modern Phototherapy: Niels Finsen and the 1903 Nobel Prize

Around the same time, Danish physician Niels Ryberg Finsen took a decisive step forward by studying light in a systematic, experimental way. He developed the first devices for filtered-light therapy and demonstrated that this method could successfully treat cutaneous tuberculosis (lupus vulgaris).

In 1903, he was awarded the Nobel Prize in Medicine for his “contributions in treating diseases with light.” This marked a symbolic turning point – a moment when light ceased to be merely an empirical practice and became an integral part of evidence-based medicine.

The Wolff Brothers’ Solaria: An Attempt to Bring Heliotherapy Into the Technological Era

As traditional heliotherapy began to fade, a new idea emerged – one that aimed to preserve its benefits while freeing it from the limits of weather, geography, and the changing seasons. In the 1970s, German brothers Friedrich and Jörg Wolff developed the first modern tanning devices.

Contrary to the later cosmetic marketing of “beauty tanning,” their original intention was grounded in health:

• enabling controlled and predictable UV exposure,
• supporting vitamin D production during the winter months,
• alleviating symptoms of seasonal depression,
• helping individuals affected by insufficient natural sunlight.

They consulted photobiologists and physicians while designing their equipment, creating a technology meant as a continuation of the work of Finsen and Rollier, but in a modern, engineered form. In many ways, they sought to “automate the sun,” to reproduce consistent, measurable conditions for therapeutic light exposure.

Why Did Heliotherapy Disappear?

After World War II, the antibiotic era began. These new medicines effectively treated many of the diseases that sunlight had once been used to manage, and heliotherapy quickly disappeared from mainstream medical practice.

At the same time, people began spending far less time outdoors, and public messaging increasingly focused on the risks of sun exposure. Over time, the positive aspects of light, once integral to medicine, hygiene, and everyday life, were largely forgotten.

A Return to Light: What Modern Science Reveals

Today, science is rediscovering what earlier physicians understood intuitively:

1. UVA releases nitric oxide, supporting cardiovascular function and blood pressure regulation.
2. Sunlight increases serotonin and beta-endorphins, enhancing mood and immunity.
3. Daytime light exposure regulates circadian rhythms and improves sleep.
4. Sunlight influences the skin microbiome and regenerative processes.
5. It is a natural source of vitamin D, though this is only one of many pathways through which it affects health.

Sunlight is neither a threat nor a cure-all. It is a biological input, one that requires balance, context, and understanding.

What Comes Next in the Series?

In the upcoming articles, we will explore in greater detail:

• Sunlight in Antiquity – Greece, Rome, Egypt, and the architecture of light
• The Sun as the Clock of Life: Rhythm, Balance, and Health in Traditional Medicine
• Florence Nightingale – how sunlight shaped modern hospital medicine
• Swiss Sanatoria – remarkable protocols and historical photography
• Niels Finsen – the birth of scientific phototherapy
• The Wolff Brothers – the origins of tanning devices and their health-driven intention
• Why Heliotherapy Disappeared
• The Return of Photobiology – what modern science now knows about light