Sunshine: Clinical Friend or Foe?

“‘But soft! What light through yonder window breaks? It is the east, and Juliet is the sun! Arise, fair sun, and kill the envious moon…'”

Shakespeare, W: Romeo and Juliet, Act II, Scene II.

When you live in Arizona, the sun is always with you. Living here makes it easy to understand that the sun has been a central factor in human existence, iconography, and a variety of religions in ancient Egypt, Indo-Europe, and Meso-America since the beginning of recorded or archaeologically defined history.1, 2

The first scientific writings concerning the benefit of sun therapy emanated from the investigations of Niels Ryberg Finsen, who won the Nobel Prize for his work with heliotherapy (Helios in ancient Greek=sun).3 Finsen observed the effect of sunlight on his own fragile health. He supplemented these personal observations with experiments on animals and eventually began a series of clinical trials using natural and artificial sunlight therapy for 2 skin conditions: smallpox and tuberculosis of the skin. The dermatologic lesions of both conditions responded to natural and artificial sunlight exposure in these experiments, eventually leading to the Nobel Prize in 1903.4

Word of Finsen's work spread rapidly throughout Europe and North America. One of the clinical scientists most interested in Finsen's work was Dr Auguste Rollier (1874-1954), a Swiss physician, who was quickly convinced of the value of Finsen's work.5, 6, 7 Rollier established numerous sunbathing clinics in the Swiss Alps and treated patients with both skin, skeletal, and pulmonary tuberculosis with sunbathing at these institutions.

Sun therapy rapidly became a popular modality in the early 20th century. Following Finsen's observations and Rollier's use of heliotherapy in many sanatoria throughout the Swiss Alps, American physicians quickly adopted these European techniques. Patients with skin, bone, and pulmonary tuberculosis received heliotherapy at institutions in California, Arizona, and even upper New York State (the celebrated Saranac hospital8). Many famous patients were treated at Saranac, including Béla Bartók, W. Somerset Maugham, Robert Louis Stevenson, and Christy Mathewson.8

In the United States, early tuberculosis sanatoria that used heliotherapy at altitude, following Rollier's model in Switzerland, were established in the Rocky Mountains of Colorado, and many American physicians touted the beneficial effects of heliotherapy for tuberculous patients. However, once effective antimicrobial therapy became available, heliotherapy for tuberculosis disappeared rapidly. Eventually, all tuberculosis sanatoria in the United States were closed or converted to other purposes.

Heliotherapy is still used for a number of conditions, although not for tuberculosis. Psoriasis, acne vulgaris, eczema, rickets, seasonal affective disorder with depressed mood, childhood failure to thrive, and jet lag are currently treated with heliotherapy by many clinicians in North America and Europe.9, 10, 11, 12

The mechanism of sunlight therapy's beneficial effects has been studied and discussed extensively in the medical literature. It seems that exposure of microorganisms to sunlight can destroy potential harmful bacteria. This is thought to be the mechanism involved in acne and cutaneous tuberculosis therapy. There also is some evidence that exposure to sunlight results in endorphin release, perhaps contributing to a sense of well-being and thereby ameliorating seasonal affective disorder. The beneficial effect of sunlight on psoriasis seems to result from suppression of immune system-mediated inflammatory responses in the skin.9, 10, 11 Current clinical thinking emphasizes that heliotherapy must be used cautiously given the fact that prolonged exposure to sunlight increases the likelihood for developing skin cancer.12 Unsubstantiated contemporary claims for heliotherapy also include benefit for patients with various types of cancer.

In conclusion, heliotherapy was one of the first successful therapeutic interventions used for patients with tuberculosis, particularly tuberculosis of the skin. This therapy has been superseded by antibiotic therapy. However, cautious heliotherapy remains an important tool in current medical therapeutics, albeit for different indications than when it was first shown to be clinically useful more than 100 years ago.

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