This year 2,000 people in Britain will die of skin cancer and a further 40,000 will be diagnosed with the disease - double the figure of ten years ago. Such statistics are particularly alarming as they come at a time when the public is increasingly aware of the causes of skin cancer. We know sunbathing is bad for us, but we just can't resist it. Winter sun holidays present particular risks, say dermatologists, because they are usually taken in tropical climes, where the sun is strongest. Many people treat them as their last chance to acquire a deep tan before going home to months of bleak, cold weather.
Winter sun seekers are also more likely to develop skin damage if they do not have a base tan - the melanin produced by light tanning gives a low-level protection against burning. But most worrying of all, by neglecting to apply sufficiently powerful sun lotions, they risk contracting the most dangerous form of skin cancer, malignant melanoma.
"Malignant melanomas tend to affect people who are covered up for most of the year then have a sudden burst of intense exposure to the sun," says Veronique Bataille, a consultant dermatologist at the Imperial Cancer Research Fund. "Most people get 50-60% of their annual sun exposure on their two-week summer holiday. Obviously, if they go away again in the winter the exposure is increased dramatically."
Ultraviolet (UV) rays, which do all the damage, make up about 3% of sunlight. There are three types of UV ray - UVA, UVB and UVC - each of which works differently. UVA penetrates the skin most deeply and is most effective at tanning, but also causes long-term cosmetic damage: wrinkling, sun spots (solar keratosis), loss of elasticity, yellowing and toughening of the skin.
UVB is known to cause erythema (sunburn) and cancer, and is strongest at altitude, putting skiers and mountaineers at particular risk. It is partially absorbed by the Earth's ozone layer which has led to (unproven) fears that ozone depletion over countries such as Australia might cause increased instances of skin cancer. UVC is potentially more harmful still, but is almost completely absorbed by the ozone layer.
UVA was traditionally thought of as non-harmful but recent studies have concluded that it, too, is carcinogenic. This is particularly worrying to users of sunbeds, which use high doses of UVA, but not UVB. Dr Bataille says: "Using a sunbed to get a base tan before a winter sun holiday is not a good idea. It won't give you the same level of natural protection as a real tan so is likely to give you a false sense of security."
Doctors in America are particularly alarmed. Eric Kraus, associate professor of dermatology at the University of Texas in San Antonio, says: "In my opinion, tanning salons are not safe at all. Tanning booths emit five times the intensity of UVA than that of natural sunlight."
Compared to other types of cancer, skin cancer is not a big killer. There are two reasons for this: some types of skin cancer are easily treated; and all are relatively easy to spot. There are three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma and malignant melanoma. The first two tend to affect people who spend long periods of time outdoors and are usually confined to areas such as foreheads, ears and back of hands. They are easily treated, although the treatment can leave scars. Malignant melanomas, by contrast, can be fatal.
A melanoma tends to spread widely on areas such as the back, thighs and feet. If confined to the skin, the chance of a cure lies between 50% and 99%, but if it spreads to the lymph nodes in the neck the survival rate beyond five years is just 30%.
People with fair skin, blue eyes, red hair, freckles and moles are more likely to develop melanomas, although the most important factor appears to be heriditary. "We all know people with fair skin who have been in the sun all their lives and have not developed skin cancer," says Dr Bataille. "We don't know why that happens but within the next five to ten years researchers hope to identify the gene that makes certain people prone to melanomas."
Modern sun screens now protect against both UVA and UVB, their strength indicated by a star rating for UVA and a SPF (sun protection factor) number for UVB. Doctors recommend that people with fair skin use creams with a SPF of at least 15 throughout their holidays.
Even slapping on large quantities of lotion may not provide complete protection. Dr Jane McGregor, senior lecturer in dermatology at St Thomas's Hospital, London, says sun screens may put us in more danger of developing cancer by encouraging us to spend longer in the sun.
Dr McGregor says a powerful sun screen may allow somebody to sunbathe for five hours without burning, compared to half an hour without protection. But the amount of harmful rays absorbed during both periods may be the same. Burning, she says, may be nature's way of telling us to seek shade.
The acceptable modern answer is to wear more clothes, particularly in the high risk hours between 11am and 2pm. Dr Lesley Walker, at the Cancer Research Campaign, advises people to wear baggy cotton clothes with a tight weave. "Flimsy cotton clothing can still allow UV to penetrate," she says. Those who cannot bring themselves to wear a long-sleeved shirt and trousers on the beach might try a siesta.
Swimmers need to take particular care as UV rays can penetrate shallow water, and are reflected off the water's surface. "Winter sun destinations are a particular risk because the sea tends to be warmer so people spend more time in it," says Dr Walker. Lotions should be re-applied every two hours, even those that claim to be waterproof. Finally, don't dig out an old tube of sun screen from the back of your bathroom cupboard - they tend to lose their efficacy after about a year.
By Mark Hodson, editor of 101 short breaks
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