One of the worst cases of sunburn I have experienced was on an overcast day. It occurred during a day trip to the island of Procida, in the Bay of Naples. I lay on the beach reading for about three hours, the sun never once penetrating the warm haze. Needless to say, I had not bothered to use sunscreen. The next few days were a painful reminder of the hidden power of the sun.
My skin was the victim of ultraviolet light, which despite the sun's apparent screening, had easily penetrated through to the beach.
There are two types of ultraviolet (UV) rays which can cause skin disease. UVA accelerates the skin's ageing process, while UVB is the main culprit in causing skin cancer. Within two hours of exposure, both UVB and UVA have caused damage to skin cells. UVA has generated free radicals which set about damaging the surface of the skin. UVB has been shown to damage DNA - the genetic material present in cells. It is this damage which ultimately leads to the development of skin cancer.
As exposure to the harmful rays continues, the skin triggers the production of melanin from cells in its deeper layers, called melanocytes. Melanin production is part of the skin's defence mechanism. It gives rise to the brown pigment craved by north Europeans during their holidays in the sun. Unfortunately a tan means skin damage has already occurred.
Continued exposure results in sunburn, by which time the damage to DNA is permanent. The melanocytes lose their ability to divide and they can turn cancerous.
There are three types of skin cancer. The most serious form, melanoma, is fortunately the least common. It is linked to prolonged exposure to the elements and usually develops on exposed skin when an existing mole begins to change characteristics. The tell-tale signs include a change in the size of a mole, a change in colour, bleeding of the mole unrelated to trauma, itchiness, lumpiness or the development of a scab. If you ever notice any of these changes to a mole on your body, seek medical advice without delay. Early diagnosis can mean a complete cure; a late diagnosis could be fatal. Dermatologists recommend that you become familiar with the moles on your skin and that you check them twice a year for any sign of change.
The most recent statistics (for 1996) from the National Cancer Registry confirm that skin cancer is our commonest cancer. There were 7,915 new cases and 82 deaths from the disease that year. Malignant melanomas accounted for seven per cent of skin cancers.
Fortunately, the vast majority of skin cancers are not life-threatening. These are primarily of two types: squamous cell carcinoma and basal cell carcinoma. Squamous cell carcinomas are caused by sunlight, and the onset can be directly linked to the quantity of ultraviolet exposure a person has had in their lifetime. It is commonest in those over 60 and appears as a painless patch, often resembling a wart, which slowly enlarges. It rarely spreads beyond the region in which it first appears.
Basal cell carcinoma is also linked to exposure to the sun's rays and has a characteristic bevelled appearance, resembling a shallow crater with raised edges. Again, its initial spread is local.
The Irish Cancer Society recently launched its Sun Smart 2000 Skin Cancer Awareness Campaign. A seminar heard that 90 per cent of skin cancers are caused by UV rays, thus rendering the disease largely preventable.
Prof John Hawk of St Thomas's Hospital in London recommended always wearing sunscreen of at least SPF 15-20 on every exposed part of the body. It is important to reapply sunscreen every two hours and immediately after swimming or exercise, he said.
Dr Gillian Murphy, consultant dermatologist at the Mater and Beaumont Hospitals in Dublin, spoke of the growing evidence that sunbeds are linked to the development of malignant melanoma. "Some sunbeds now have more UVB - the most harmful of the UV rays - than previously," she told the Sun Smart launch.
Dr Murphy called for more controls on the use of sunbeds. They should be limited in session length, the number of sessions per year and only available to those over 18 years. She would like to see sunbed operators legally obliged to undertake a recognised training course and to hold adequate public liability insurance. But given the proven link between UVB and skin cancer, a largely preventable disease, is it not time to consider a complete ban on sunbed use?
Contact Dr Houston at mhouston@irishtimes.ie or leave messages at 01-6707711 ext 8511