This summer, SPFs are everywhere in pharmacies and cosmetics aisles. Using a sunscreen with a high SPF won't prevent you from tanning.
Conversely, applying a high SPF doesn't mean you don't need to reapply your sunscreen regularly. While we know that these products are related to sun protection, we often don't know how they work and how to choose the right ones.
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What are SPFs?
SPF (Sun Protector Factor) is an index that measures a product's level of protection against sunburn caused by UVB rays. More specifically, SPF corresponds to the difference between the minimum erythemal dose (MED) of skin protected by a sunscreen product - the smallest amount of light capable of triggering sunburn at the site of exposure - and that of unprotected skin. In other words, SPF indicates the length of time protected skin can withstand the sun before it begins to burn.
SPF is also known by the French acronyms FPS, Sun Protection Factor, or IP for Protection Index.
How do I choose my SPF?
SPFs meet 4 levels of sun protection:
- 6 to 10: low protection level
- 15 to 25: medium level of protection
- 30 to 50: high protection level
- 50+: very high level of protection
Each index corresponds to the time it will take for the skin to redden from the moment it is exposed to the sun. For example, if your skin usually reddens after 15 minutes of unprotected exposure, with an SPF 20, these 15 minutes will theoretically be multiplied by 20. It will then take the skin, no longer 12 minutes, but 5 hours to get the same sunburn.
SPF can also be translated as the percentage of UVB rays that are blocked, the rays responsible for sunburn. For example, an SPF 20 is considered to block about 92% of UVB rays, while an SPF 30 blocks about 95% of them, and an SPF 50 blocks about 98% of them.
Please note, however, that these data are indicative and do not take into account the quantity of product applied, your phototype and the power of the UV rays at the time of exposure.
Which SPF for my skin?
The choice of SPF depends largely on your sensitivity to the sun, which is itself directly linked to your skin color. Remember that skin color varies depending on its melanin content. The more melanin an individual produces, the darker their skin will be. There are 6 phototypes: 1 corresponding to a very light complexion and 6 to dark brown to black skin. However, since the role of melanin is to protect the skin against ultraviolet rays, light skin is therefore more sensitive to the sun.
How to use sunscreen properly?
To ensure the photo-protective action of a sunscreen and get the most out of it, it is advisable to follow certain application procedures:
- apply your cream generously before exposing yourself to the sun - a reduced quantity of sunscreen reduces its protective capacity;
- reapply every two hours to maintain its level of protection, particularly after swimming and in case of perspiration or rubbing with a towel or clothing;
- don't forget sensitive areas like ears, hands, feet or even hair roots;
- avoid prolonged exposure even if you use sunscreen and prefer not to expose yourself at all between 12 p.m. and 4 p.m. The sun's rays are particularly dangerous for the skin at these times, regardless of your phototype.
SPF 50 or 50+ can provide a false sense of security, suggesting that a single application will provide very long-lasting protection. Regardless of the SPF, its effectiveness is temporary. Finally, no cream can guarantee total protection against UVB rays, which is why it's important to follow best practices and don't hesitate to use a few accessories like a wide-brimmed hat or a light, loose-fitting shirt to protect your skin.
Get a beautiful tan in complete safety!