As surely as Easter comes every year, the discussion about sunscreens flourishes in the media. Norwegians are a sun-loving nation and have the highest number of cases of mole cancer (melanoma) in the world, after Australia. The main cause of skin cancer, both the potentially dangerous mole cancer, but also other types of skin cancer, lies in sun damage.
It is the ultraviolet rays (UV rays) in sunlight that cause damage to the epidermis that can develop into skin cancer over time. Sun damage often goes back a long way.
The ultraviolet rays that we are exposed to are mainly UVA and UVB. UVA rays penetrate deeper into the skin and cause pigmentation and ageing, but are probably also the main cause of mole cancer.
UVA rays are concentrated in large quantities in solariums, which is thus a contributing factor in the number of cases of mole cancer. UVB rays hit the skin more superficially, but are still stronger and can cause sunburn. At the same time, UVB rays also promote the formation of vitamin D and are one of the main causes of less serious forms of skin cancer, such as basal cell cancer and squamous cell cancer.
When you use sunscreen with factor 50, it means that it takes 50 times longer for the skin to turn red (minimal erythema dose) compared to being without sunscreen. The ratio figure 50 must nevertheless be interpreted with caution as it is based on research and calculated under controlled conditions.
How long you can be in the sun before you get sunburned depends on your skin type, how close to the equator you are, whether you stay in higher altitudes, whether you lie on a white sandy beach or are on the water where the reflection of the sun's rays amplifies the effect.
The sun factor is measured on fresh skin when you apply the sunscreen with a thickness of 1 millimeter and measure the time it takes before you turn red (minimal erythema dose, also known as MED). The problem is that we usually apply the sunscreen in a much thinner layer than when the sun factor is tested.
If we apply only half as thick, we also reduce the solar factor by 50%. If we lubricate only a quarter of the thickness, we reduce the solar factor by 75%. It is therefore wise to start with as high a solar factor as possible to reach a real factor corresponding to factor 15, which the Norwegian Cancer Society recommends.
The main factor listed on the tube concerns the protection against UVB. The authorities have decided that the UVA protection must be at least one third of the factor that the tube shows against UVB. This is another reason to start with the highest possible UVB factor in order to arrive at a usable protection against UVA.
Even the highest sun factors release so much UVB rays through that you get color and that you form vitamin D. It takes a little longer, but you avoid getting sunburned.
Every year the media write about the disadvantages of using sunscreen without focusing on the positive effects. It is mentioned that sunscreens contain hormones, harmful chemical substances, allergens and even lead to skin cancer. We dermatologists experience very few problems when using sun creams and the positive effect of sun protection is undoubtedly much higher than possible side effects. Sunscreen is a fresh product and should be renewed every year.
