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Sunbathing for Experts

Sunbathing for Experts

Looking to enjoy the sun this summer and get a nice tan? Then be smart and apply sunblock.

5 minutes
10 August 2020

Looking to enjoy the sun this summer and get a nice tan? Then be smart and apply sunblock. Because the sun’s ultraviolet rays are a double-edged sword. ‘Your skin needs sun, but too much is harmful,’ says KU Leuven dermatologist Marjan Garmyn.

Sunbathing: it boosts your mood and ensures your skin can produce vitamin D. And you need those vitamins for strong bones and teeth. But the positive effect of sunlight on the skin is short-term, whilst ultraviolet (UV) light damages your skin quite quickly – after only fifteen minutes for those with very sensitive skin types.

So grab your sun cream or spray and take a good look at the packaging. Does the product offer protection against UVB and UVA? About 95 percent of all UV rays are UVA, ultraviolet A-rays (with the A for allergy and aging). These are sunrays that can give you a sun allergy and age your skin. There’s no escape because UVA light passes through everything, including glass, and it penetrates deep into the skin. UVA gives you a tan quickly, but briefly, because the pigment cells in your skin release the natural pigment melanin. As an illustration, tanning beds use UVA rays.

Tanned, burnt

The other five percent UV rays that reach us consist of UVB (with the B for bronzing and burning). These are sunrays that cause some people to turn as red as a lobster after a short while whilst others enjoy a nice brown complexion. UVB causes your skin to produce more pigment. This ensures a brown colour that lasts longer and that offers you a certain amount of protection. But, unfortunately, that’s not possible without damage.

UVB causes direct damage to the DNA in your skin cells, explains dermatologist Marjan Garmyn from KU Leuven and UZ Leuven. ‘Small changes to DNA can lead to mutations; if skin cells with a mutation start to divide, it leads to permanent damage and eventually cancer. With UVA, the DNA is not directly damaged, but it is damaged in an indirect way by other parts of the cell.’

Professor Garmyn at work
Professor Garmyn at work

Accumulated damage

The greatest danger from both UVA and UVB is skin cancer. The deadliest form of skin cancer is melanoma, a malignant tumour that develops in the epidermal pigment cells and that can spread. Other forms are squamous cell carcinoma and basocellular carcinoma. ‘Simply put, you get the last two types of skin cancer mainly from cumulative damage to the skin that builds up year after year, while melanoma is acute damage, such as a sunburn from the first direct sun exposure after winter.’

Your skin type plays a major role in these skin cancers. Do you have pale skin, blonde or red hair and blue eyes? Then you are naturally less protected against damage from UV light. ‘This kind of person doesn't tan and, at most, produces freckles. They certainly cannot be permitted to get a sunburn. The same goes for other risk groups: children and people with a lot of moles or a history of melanoma in the family.’

Reapply, reapply, reapply

So be smart and protect yourself. ‘Tanning beds are out of the question. If you’re just sunbathing, avoid becoming red. Use a sunscreen that protects against both UVA and UVB, with a sun protection factor (SPF) of at least 30, and for higher risk groups use at least 50. Apply regularly every two hours, even more often if you’re in a place where UV light is reflected – in the water, on the beach, in the snow. Also note the date. Your skin is especially sensitive to the first sun after winter. And in the summer, the intensity of the UV in the sunlight – the UV index – is highest between 12.00 and 14.00.’

In the last ten years, the malignant melanomas numbers in Belgium – the most dangerous skin cancer – have risen sharply: from 1,500 cases in 2004 to 3,300 in 2017. ‘It is more common, but fortunately mortality rates are not increasing. People go to the doctor faster and melanoma is easier to treat at an early stage.’ Do you have a spot on your skin that changes shape or colour, loses its symmetry or is starting to turn different colours? Then don’t hesitate, go to the dermatologist for an examination.


When examining spots, the skin doctor uses a dermatoscope – a high-power illuminated magnifying lens – that is placed directly on the skin. Applying a drop of oil or water to the lens makes the top layer of skin slightly transparent and allows the doctor to see through the skin. This makes structures visible that cannot be seen with the naked eye. In this way the dermatologist can search for abnormal structures or colours.

The technology of the dermatoscope is still developing, explains Professor Garmyn. ‘KU Leuven and UGent are working together with the Kortrijk imaging company Barco on a smart dermatoscope. The device looks like a smartphone, but it’s actually a skin scanner that can take very detailed photos of skin lesions. This is done with white light with a normal dermatoscope. With this device, multispectral light is also used, allowing you to look at different depths in the skin and to zoom in on, for example, blood flow or pigment. All of these images are forwarded to an online database. Thanks to the use of artificial intelligence, an alarm bell should ring faster in the case of skin cancer as the AI learns from older photos and searches for patterns that indicate malignancies.’

The dermatoscope in use
© UZ Leuven

Vitamin D

In addition to research into technology, KU Leuven is currently conducting a unique, long-term study into the role of vitamin D in relapses of melanoma patients. In addition to age, gender, genetic factors and your immune system, the prognosis mainly depends on the thickness of the tumour. The deeper a melanoma has penetrated the skin, the worse the prognosis for the patient. ‘But vitamin D also appears to be a factor: with a vitamin D deficiency at the time of diagnosis, the prognosis is worse.’

The question now is whether it makes sense to give extra vitamin D when diagnosing melanoma. ‘This should be evident in the coming years from our long-term study with some 500 patients. The study is double-blind and placebo-controlled; one group of patients receives a placebo, the other group receives vitamin D, without researchers or patients knowing which group is which. After all, you have to be able to measure whether it’s really vitamin D that has a protective effect and not some other factor such as a healthier lifestyle.’ Both the study and final analysis will be completed within the next two years.