Sun tans are caused by specialized cells in the skin called the melanocytes. They produce the pigment melanin, which makes the skin appear brown. Though a tan is thought to provide some protection from the ultra-violet radiation, it is also known to cause skin damage. This damage causes not only age-related signs but can also lead to skin cancer. Ultra-violet radiation comes from either the sun or artifical sources like tanning booths or sun beds.
Skin Cancer, the Sun and Tanning Booths
It is not only sunburn that causes damage but cumulative exposure to ultra-violet radiation. Skin damage can occur even without the erythema or the redness that is associated with sunburn. UV radiation, particularly UVA and UVB, are carcinogens. When the sun rays hit the skin, the UV rays can be absorbed by the skin's cells. The rays can cause damage to the cell’s DNA, resulting in mutations which can lead to cancer. Skin cancer is on the increase with the WHO estimating that 130,000 malignant melanomas, the most serious and often fatal skin cancer, occurring worldwide. Other skin cancers linked to UV radiation include squamous cell carcinomas and basal cell carcinomas.
Tanning beds and booths are known to produce both UVA and UVB. This artificial UV radiation similarly to UV radiation from the sun can cause alterations in the cells genes which can result in skin cancers and/or photoaging. The National Cancer Institute estimates that women who use a tanning bed more than once a month have a 55 percent increased risk of developing the most dangerous form of skin cancer, melanoma.
Ageing, the Sun and UV Radiation
UVA can penetrate deeper into the skin's structure into the dermis and damage the skin's structural proteins such as collagen. The cells can produce enzymes which break down collagen, resulting in wrinkles due to the lack of collagen. Exposure to UV radiation can result in hyperpigmented areas or even areas where the skin has lost its color. The skin can become leathery, thick and wrinkled.
UV radiation can cause skin lesions called actinic keratoses. These lesions are often found in areas which are regularly exposed to the skin such as the face, hands and necks. They are considered a risk factor in developing squamous cell carcinoma. They are scaly crusty lesions which need to be checked by a doctor.
UV Radiation, Eye Damage and Immunity
UV radiation not only causes damage to the skin but also to the eyes. This damage can result in cataracts, a benign growth in the corner of the eye, and skin cancers around the eye. Damage to the eye can be caused by reflection of the sun rays from snow, sand and sea, for example. This damage or snow blindness, though temporary, can be extremely painful.
The skin is the largest organ in the body and is far from passive. The skin contains a number of cells which are involved in the body’s immune response. Damage caused by the sun to these specialized cells can prevent the skins immune cells from signalling to the body of a foreign body. It is also thought that damage to these cells can be involved in the development of skin cancer.
Preventing Sun Damage
Though UVB causes sunburn, it is both UVA and UVB which cause damage. A sunscreen should be selected which protects against UVA and UVB. Many dermatologists recommend a SPF of at least 30. Sunscreen protection is measured when applied at a thickness of 2mg/cm2. Therefore sunscreen should be applied liberally and should be reapplied regularly. Sunscreens should not be used to extend the length of sun exposure
Sunscreens do not block out all UV radiation and the best protection is avoiding the sun at its peak between the hours of 11am and 3pm. Covering up with clothes, hats and sunglasses are also useful, though it must be realised that clothes, especially those with a loose weave, will allow UV radiation to still reach the skin. It is possible to buy clothing with an SPF rating .
Sources:
Anti-Inflamm Anti-Allergy Agents Med Chem, UV Induced Skin Immunosuppression, Amerio P., et al, 8 (1) 2009
Arch Dermatol, Sun Exposure, Sun Protection, and Vitamin D. Thieden E., et al. 141(12) 2005
Cancer Epidemiol Biomarkers Prev, Point:Sunscreen Use is a Safe and Effective Approach to Skin Cancer Prevention. Green AC., Williams G.M. 16 (10) .2007
JAOA, Ultraviolet Radiation: Sun Exposure, Tanning Beds, and Vitamin D Levels. What You Need to Know and How to Reduce Your Risk of Skin Cancer. Scarlett W.L., 103 (8) 2003
National Cancer Institute, "NCI Health Information Tip Sheet for Writers: Artifical Tanning Booths and Cancer". (accessed July 16 2010)
Skin Cancer Foundation, "Sunscreen" (accessed July 16 2010)
Sunprotection.net, "Sunscreen" (accessed July 16 2010)
World Health Organization," Sunbeds, Tanning and UV Exposure". (accessed July 16 2010)
Kerstin Rolfe - Kerstin Rolfe is a research scientist who writes in her free time because she loves writing. She was awarded a PhD from the University of ...
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