Do you know how sunscreens work?

In the summer, ultraviolet (UV) radiation hits us with greater intensity, so protecting your skin from its harmful effects is even more important. There are two main types of UV radiation: UVA and UVB, and both can cause skin cancer and DNA damage. However, they are different: in layman’s terms, UVA rays are associated with aging, or “aging” in English, while UVB rays are associated with burns.

UVB affects the epidermis, the outermost layer of the skin, so they are responsible for tanned skin, but are also responsible for sunburn, the leading cause of skin cancer.

UVA rays, which correspond to 95% of ultraviolet rays that reach the planet’s surface, are most responsible for premature skin aging, in addition to causing dark age spots and sun allergies. They also have the ability to penetrate deeper into the skin, reaching the cells of the dermis, the deepest layer, and can pass through clouds and glass. Therefore, despite being painless (unlike UVB), they are not harmless.

It is against UVB rays that regularly purchased sunscreens protect. Data from the Portuguese League Against Cancer shows that about 53% of Portuguese apply sunscreen only after they feel a burning sensation on their skin, and 40% do not reapply the product after the first application. However, its use is necessary to prevent skin cancer and to maintain skin hydration.

Experts recommend that during your first time in the sun, use sunscreens with a sun protection factor (SPF or SPF) equal to or greater than 30. This SPF is listed on all sunscreens, indicating one of four levels of protection: low (a factor of 6 up to 10), medium (15 to 25), high (30 to 50) and very high (50+).

But what is FPS?

SPF is related to protection against UVB rays, not UVA rays. It is determined by taking into account the amount of UV radiation required to cause sunburn, with or without sunscreen. In other words, if skin is unprotected and sunburn occurs 10 minutes after sun exposure, the same skin will get sunburned 100 minutes later if you apply a sunscreen with an SPF of 10, and the same calculation is made for the rest of your skin. (multiply minutes it takes to get a sunburn from SPF).

However, this protective effect does not increase linearly with increasing FPS. In other words, if an FPS of 10 can reduce UVB radiation by about 85%, an FPS of 15 blocks this radiation by about 93%, and an FPS of 20 by about 95%. FPS 100, which is the highest, can guarantee 99% protection from radiation.

There are still no sunscreens that guarantee complete protection from the sun’s harmful rays and There are also no products of this type that are completely waterproof (besides the fact that UV radiation has the ability to penetrate water up to a depth of 50 cm). Therefore, sunscreen should be reapplied after each swim.

On the reality of sunscreensThey are usually good for one year after opening (some brands extend this), but you should always check the package directions. The way these products are stored after use is also important – they should not be exposed to direct sunlight or very high temperatures as they may lose their effectiveness, and their odor and texture should be kept in mind for some time afterwards.