Sun Therapy
Medicinal Profile of
Sun Therapy
Sun Therapy has been a vital human practice across history, celebrated for its ability to warm the body, lift mood, and sustain life through the synthesis of vitamin D. Sun therapy is the intentional use of sunlight as medicine. Traditional cultures recognized the sun as both a healer and a force to respect, vital in moderation, harmful in excess. Scientifically, controlled sun exposure regulates circadian rhythm, strengthens bones, supports immunity, and enhances emotional well-being.
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Ancient Civilizations
Greeks and Romans used heliotherapy (sun therapy) as part of medical regimens; Hippocrates’ “Solarium” on Kos Island was built specifically for patient sunbathing.
Indigenous peoples worldwide (North America, Mesoamerica, Africa, Australia) incorporated the sun into rituals of fertility, growth, and renewal.
Traditional Healing Systems
Ayurveda considered the sun (Surya) a source of prana (life force). Sunbathing and morning light gazing were used to align body rhythms.
Traditional Chinese Medicine (TCM): Sun exposure balanced yin (cold/dark) and yang (warm/light) energies, important for vitality.
Unani Medicine: Recommended controlled sunbathing for melancholy and skin conditions.
Modern Revival
In the 19th and early 20th centuries, physicians prescribed sunbathing for tuberculosis, rickets, and depression.
Today, moderate sun exposure is recognized for its role in vitamin D synthesis, circadian regulation, and immune health.
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Stimulating – increases energy, activity, and circulation.
Expansive – opens blood vessels and energizes movement.
Warming – raises body temperature, dispels cold.
Nourishing – promotes vitamin D synthesis, strengthens bones and immunity.
Illuminating – regulates circadian rhythm and uplifts mood.
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Affinities describe the natural “pull”, a substance or practice, has with certain organs, tissues, or systems in the body. Think of it like a magnet: every herb, food, or functional agent seems to “go to” certain areas first, where it has the strongest effect.
Primary Affinities
Endocrine System – regulates melatonin, serotonin, and vitamin D metabolism.
Skeletal System – supports calcium absorption and bone health.
Secondary Affinities
Immune System – enhances surveillance and immune balance via vitamin D.
Nervous System – regulates circadian rhythm and mood.
Circulatory System – improves vascular dilation and blood pressure regulation.
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Terrain indications describe the patterns inside the body where a remedy or practice is most useful.
👉 To learn more about these patterns in depth, read this blog.
Primary Indications
Hypofunction Terrain – when processes are running too slow or weak (coldness, sluggish metabolism, low energy). Action: Sun’s warmth stimulates metabolism, raises energy, and restores activity. Application: 15–30 minutes of morning or late afternoon sun, 3–5x per week. Midday may be used briefly (5–10 minutes) in colder months.
Fluid Congestion – when fluids stagnate and create heaviness or swelling. Action: Gentle sun exposure increases circulation, reduces fluid buildup, and supports elimination through light sweating. Application: 15–20 minutes in late morning or afternoon, avoiding peak sun to prevent overheating.
Secondary Indications
Mild Hyperfunction-Hypofunction overlap) – when low light and sluggishness lead to sadness or irritability. Action: Sunlight boosts serotonin and dopamine, lifting mood and regulating circadian rhythm. Application: 20–30 minutes of morning light, daily if possible, with face and eyes (indirect exposure) uncovered for circadian entrainment.
Erratic Regulation – when rhythms of sleep, energy, or hormones swing between highs and lows. Action: Daily sun anchors circadian rhythm, balancing melatonin and cortisol cycles. Application: Morning sun within 1 hour of waking, 10–20 minutes daily, even on cloudy days.
Emergency Indications
Seasonal Affective Dysregulation (SAD) – winter depression or low energy due to lack of sunlight. Action: Intentional sunlight or light therapy lamps restore missing light input, stabilizing mood and rhythm. Application: 30–45 minutes of outdoor morning light (or equivalent via lamp) during low-sun seasons.
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Vasodilation & Circulatory Training
Heat causes blood vessels to dilate, increasing circulation and lowering vascular resistance.
This improves delivery of oxygen and nutrients while training vessels for better tone and flexibility.
Hyperthermic Conditioning (Heat Stress Response)
Sauna temporarily raises core body temperature → mimics a mild fever.
This activates heat shock proteins (HSPs) which protect cells from stress, repair damaged proteins, and support resilience.
Immune Activation
Heat stress stimulates white blood cell activity and enhances immune vigilance.
Mimicking fever helps the body more effectively fight off infections.
Sweating & Detoxification
Sweating supports elimination of water-soluble toxins, heavy metals, and metabolic byproducts.
Enhances clearance of excess sodium and fluid, easing congestion patterns.
Cardiovascular Training
Heart rate rises similarly to light–moderate exercise (100–150 bpm).
Repeated sauna use improves cardiorespiratory fitness, reduces blood pressure, and strengthens heart function.
Nervous System Regulation
Heat initially activates the sympathetic nervous system (fight-or-flight), but the recovery phase enhances parasympathetic activity (rest-and-restore).
This shift improves relaxation, stress resilience, and sleep quality.
Endocrine & Hormonal Effects
Temporary increase in growth hormone (GH) which supports repair and metabolism.
Reduces cortisol after sessions, lowering stress burden over time.
Metabolic Activation
Heat exposure increases insulin sensitivity and glucose uptake by muscles.
Supports weight regulation by enhancing metabolic flexibility.
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Hyperfunction / Hyperreactivity Terrain
Caution: excess sun worsens overheating, irritability, or inflammatory flares. Reason: adds stimulation to a system already running too fast.
Skin Sensitivity & Conditions
Contraindication: active skin cancers, precancerous lesions, or conditions worsened by UV (lupus, severe eczema, photosensitive rashes). Reason: UV can aggravate or accelerate tissue damage.
Photosensitizing Substances
Caution: certain medications (antibiotics, diuretics, retinoids), and herbs (St. John’s Wort, citrus oils) make skin extra sensitive to sunlight. Reason: higher risk of burns or reactions.
Collapse Terrain / Severe Hypofunction
Contraindication: weak, fragile states with low reserves. Reason: prolonged sun can cause fainting, dehydration, or collapse.
Overexposure Risks
Contraindication: long, unprotected exposure at midday sun. Reason: leads to sunburn, premature aging, and higher cancer risk.
Eye Safety
Caution: never look directly into the sun (retina damage). Reason: circadian entrainment comes from light entering the eyes indirectly.
Medicinal Actions of
Sun Therapy
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Vitamin D synthesis – sunlight (UVB) stimulates vitamin D production in the skin, regulating calcium balance, bone health, and immunity.
Hormone regulation – increases serotonin (mood uplift), balances melatonin (circadian rhythm).
Cortisol balance – morning light helps set healthy daily cortisol rhythms.
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Bone strengthening – vitamin D improves calcium absorption and bone mineralization.
Fracture prevention – adequate sunlight reduces risk of osteoporosis.
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Immune modulation – vitamin D regulates T-cell activity, reducing autoimmunity risk while strengthening defenses.
Inflammation balance – sunlight exposure can help reduce chronic low-grade inflammation.
Barrier defense – supports skin’s immune surveillance.
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Mood elevation – boosts serotonin and dopamine, improving mental well-being.
Circadian entrainment – morning light sets internal clocks, stabilizing sleep/wake rhythms.
Cognitive clarity – regulates neurotransmitters tied to focus and memory.
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Vasodilation – sunlight triggers nitric oxide release in vessels, lowering blood pressure.
Cardiovascular support – moderate exposure improves vascular tone and reduces risk of hypertension.
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Surface renewal – controlled UV stimulates turnover of skin cells.
Antimicrobial effect – UV light reduces certain pathogens on skin.
Skin Vitality – gentle exposure enhances complexion (when not excessive).
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Holick, M. F. (2004). Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. American Journal of Clinical Nutrition, 80(6), 1678S–1688S.
Juzeniene, A., & Moan, J. (2012). Beneficial effects of UV radiation other than via vitamin D production. Dermato-Endocrinology, 4(2), 109–117.
Lucas, R. M., et al. (2019). Sun exposure and health: From vitamin D to skin cancer. Medical Journal of Australia, 211(7), 324–325.
Hossein-nezhad, A., & Holick, M. F. (2013). Optimize dietary intake of vitamin D: An epigenetic perspective. Current Opinion in Clinical Nutrition & Metabolic Care, 16(6), 567–579.
Wacker, M., & Holick, M. F. (2013). Sunlight and vitamin D: A global perspective for health. Dermato-Endocrinology, 5(1), 51–108.
Wirz-Justice, A., et al. (2004). Light therapy for seasonal affective disorder and other psychiatric conditions. Journal of Affective Disorders, 84(2-3), 125–133.
Diffey, B. L. (2010). Is casual exposure to sunlight effective in providing vitamin D in the UK? British Journal of Dermatology, 163(5), 1057–1068.
Norval, M., & Halliday, G. M. (2011). The consequences of UV-induced immunosuppression for human health. Photochemical & Photobiological Sciences, 10(5), 791–801.
🌞 Note on Sun Allergy
Some people have a condition called polymorphous light eruption (PMLE) or “sun allergy,” where sunlight triggers rashes, bumps, or hives on the skin. For these individuals, even short exposures can cause discomfort.
👉 If you have a sun allergy, avoid direct sunlight and consider working with filtered light or gentle morning/evening exposure only under guidance.
Supportive tips for better handling sunlight:
🌼Reduce immunological load – strengthen tolerance by addressing allergies, gut imbalance, or chronic inflammation.
🌼Build tolerance gradually – start with short exposures (1–2 minutes) at sunrise or sunset, slowly increasing.
🌼 Nourish the skin from within – antioxidant rich (stabilizing) foods like berries, leafy greens, omega-3s, demulcent herbs like marshmallow root, and hydration improve skin resilience.
🌼Topical protection – mineral sunscreens, light clothing, and hats can reduce reactivity without blocking all beneficial light.
