How sunlight causes skin cancer


According to the Australian Cancer Council almost all skin cancers - approximately 99% of non-melanoma skin cancers and 95% of melanomas - are caused by too much UV radiation from the sun, sun beds and sun lamps.

Over the past 20 years the number of people in the world who develop melanoma – the deadliest form of skin cancer- has more than doubled, according to CANSA.

Cancer Research UK, maintains that more than 80% of melanoma cases could be prevented by avoiding sunburn which is a clear sign that the DNA in your skin cells have been damaged. The often painful accompanying symptoms are simply due to your body's attempts to repair the sun damage and experts warn that just one severe sunburn during the first 15 years of your life can double your risk of developing skin cancer.

Overexposure to ultraviolet rays while lying in the sun is the leading cause of skin cancer and sun beds and sun lamps are just as dangerous. Skin cancer develops in the cells in the top layer of your skin, the epidermis UV radiation includes both UVA and UVB rays which are able to penetrate your skin and cause permanent damage to the cells below.

UVA penetrates deeply into your skin (the dermis) causing genetic damage to cells, photo-ageing (wrinkling, sun spots) and immune-suppression.

UVB penetrates into the epidermis, causing damage to the cells. UVB is responsible for sunburn – a significant risk factor for skin cancer.

If your body is unable to repair this damage the cells can begin to divide and grow in an uncontrolled way. This growth can eventually form a tumour. Melanoma and non-melanoma skin cancers can be invasive as they grow across the surface of your skin and sometimes down through the layers. If the tumour grows through the wall of a blood or lymph vessel, cancer cells can then break off and spread to other parts of your body. That's why it's so vital to check and detect skin cancer early.

South Africa has the second highest incidence of skin cancer in the world after Australia as well as one of the highest numbers of malignant melanomas with 1 in 196 people being diagnosed annually, mostly aged between the ages of 20 and 40. Anyone can get skin cancer but you are at a higher risk if you have fair skin, light eyes and hair, and a personal or family history. Remember that even though skin cancer that's diagnosed and treated early has a good prognosis, prevention is always better than cure. So adopt these sun-safe strategies for both you and your family to protect your skin from the sun:

  • Always use sunscreen with a sun protection factor (SPF) of at least 30. Apply 30 minutes before going outside, and reapply every two hours or after swimming or sweating. Research has shown that regular sunscreen use in children can decrease their cancer risk by 80%.
  • Always keep babies and very young children out of direct sunlight.
  • Always wear a hat with a wide brim that shades your face, neck, and ears.
  • Always wear sunglasses that block UV radiation to protect the skin around your eyes.
  • Always try to avoid being out during the hottest parts of the day: between 10:00 and 16:00. And remember that UV radiation is reflected by sand, water, snow, and ice and can penetrate windshields and windows so take appropriate precautions.

SA Melanoma Advisory Board, Annals of Internal Medicine June 2013, The Skin Cancer Foundation (US), the Journal of the American Academy of Dermatology, CA: A Cancer Journal for Clinicians, JAMA Dermatology.


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