If you are concerned about taking care of your skin, you will know that protecting yourself from the sun daily is the most important step in your beauty routine. You will also be familiar with the letters SPF (Sun Protection Factor) or Sun Protection Factor. Today, we want to explain to you how it is calculated, what it really means and why it is important to understand how it works to prevent premature aging and protect your skin from UV rays.
What does SPF indicate?
Indicates the level of sun protection and how long a sunscreen increases your skin's natural resistance to sunburn compared to not using it. For example, an SPF 30 sunscreen multiplies your defense capacity against UVB rays by 30.
How is SPF calculated?
Through clinical tests, the amount of UVB radiation necessary to generate a skin redness reaction (erythema) is evaluated, comparing skin protected by the product and exposed skin without protection.
Does the SPF specify how long I can be exposed to the sun?
It depends. To calculate it, you need to know how long it takes for your skin to turn red without sun protection. Multiply those minutes by the SPF number and you will get the approximate time you can sunbathe without burning. Of course, keep in mind that factors such as time of day, altitude or skin type can modify the minutes of safe exposure.
PRO TIP:
As there are so many variables, it is best to apply the sunscreen half an hour before exposing yourself to the sun and reapply every two hours or every time you sweat or bathe.
Does the SPF say how much solar radiation it blocks?
SPF does not measure total sun protection against all solar radiation, but specifically against UVB rays, which are mainly responsible for sunburn. The higher the SPF number, the longer the protection and safe exposure time.
In general, you could say that SPF 30 blocks around 96-97% of UVB rays, while SPF 50 can block up to 98%.
It is important to clarify that no SPF blocks 100% of solar radiation. Furthermore, SPF does not measure protection against UVA rays, which are responsible for premature aging and other skin damage. For this, it is necessary to ensure that the sunscreen includes protection against both types of radiation.
What does “broad spectrum” mean?
Although it is not necessary to guarantee an effective defense against UVA and UVB radiation, this term does indicate that the product has passed a specific test that certifies this double protection. While UVB is primarily responsible for visible sunburn, UVA penetrates deeper into the skin and is associated with premature aging and skin cancer.
How do I know that the SPF of my product is reliable?
The SPF certification is based on tests carried out in specialized and independent centers. In Europe, in vivo evaluations—where volunteers apply sunscreen and are exposed to controlled UVB radiation—must comply with the ISO 24444 standard. These tests are carried out in laboratories certified under the ISO 9001 quality management standard.
In addition, there are complementary in vitro methods, such as those established in ISO 24443, which allow the evaluation of protection against UVA rays and help to guarantee the overall effectiveness of the product according to current regulations.
