Health Effects of UV Radiation

Exposure to UVA and UVB radiation can cause skin damage, eye damage and weaken the body's immune system. However, UV radiation can also be beneficial. We require UVB for the production of vitamin D₃ in our bodies and it can be used in controlled quantities to treat certain skin conditions.

On this page:

• Skin Damage
• Eye Damage
• Immuno-suppression and Infectious Disease
• Vitamin D₃ production
• Treatment of skin conditions

Skin Damage

A tan is visible proof that your skin has been damaged from ultraviolet radiation. Tanning is your skin's response to overexposure to UV radiation. Tanning occurs when UV radiation is absorbed by the skin, causing an increase in the activity and number of melanocytes, the cells that make the pigment melanin. Melanin helps to block out damaging UV. Sunburn occurs from overexposure to UV: the skin turns red and may become hot and painful or even swell and blister.

Overexposure to ultraviolet radiation also causes premature ageing effects such as skin wrinkling and hardening (leathery skin), blotchiness, loss of elasticity, dark patches (age spots" or "liver spots") and precancerous skin changes (called actinic keratoses).

Skin damage caused by the sun is cumulative, which means that long term, daily exposure to sunlight adds up. UV exposure causes damage in the DNA of our skin cells. Either those damaged cells die or they get repaired by the cell's own repair mechanism. But if the damage is too severe and the cells cannot repair it adequately, this can result in the development of skin cancer.

For more information regarding skin damage, consult our publications entitled "Preventing Skin Cancer", "Sunscreens", and "Ultraviolet Radiation From the Sun".

Eye Damage

Overexposure to ultraviolet radiation may cause painful temporary injuries to the eye called photokeratitis and photoconjunctivitis. Reflections off water, sand, snow, concrete and glass can inflame the cornea and conjunctiva within minutes. This is like burning the sensitive, skin-like tissues of the eyeballs and eyelids. "Snow blindness" is a term used by skiers and snowboarders when they experience this after a day on the slopes without goggles. Remember to wear those shades - with 100% UV protection, of course. Exposure to solar UV, acute or long-term, direct or reflected, can prematurely age the lens, causing cataracts, growth of pterygium, macular degeneration, and eyelid cancers.

For more information on eye damage caused by UV, go to our publication entitled "Sunglasses".

Immuno-suppression and Infectious Disease

Hanging out in the sun can also have negative impacts on the immune system - the body's natural defence against disease. UV can suppress resistance to bacterial agents and enhance risk of infection, including meningitis. In addition, UV radiation can cause smallpox lesions to grow and reactivate Herpes simplex Virus I and II (manifested in cold sores).

Vitamin D₃ Production

Vitamin D₃ helps the body absorb calcium and phosphorus and plays a crucial role in skeletal development, immune function and blood cell formation.

Exposure to the UVB part of sunlight is essential to trigger vitamin D₃ formation in the skin. UVB converts 7-dihydroxy-cholesterol into vitamin D₃, which is than converted by the liver and the kidney into its active form. Dietary sources of vitamin D₃ include fish, eggs, and fortified foods (i.e. milk, flour and cereals).

For most people, vitamin D₃ deficiency is unlikely. However, during the winter months (i.e. October-March), solar UVB levels in Canada are not sufficient enough for vitamin D₃ formation in the skin. Some highly pigmented individuals, adults over the age of 50, breastfeeding women, and those living in higher altitudes are at higher risk of lower blood levels of vitamin D₃. They should consult a health care practitioner to see if vitamin D₃ supplements are necessary.

Treatment of Skin Conditions

UV radiation has been used to successfully treat a number of diseases, including rickets, psoriasis, eczema, jaundice, lupus vulgaris and vitiligo.