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Signification du sigle SPF sur les soins solaires.

SPF 20, 30, 50: what does this mean?

You often see SPF 20, 30 or 50 printed on sun cream packaging. These figures are also regularly found on pots or tubes of certain skincare products and makeup. Cosmetologists advise that we pay attention to the numbers that accompany the mention of “SPF”. But what do they mean? And why are they important?

Published November 29, 2022, by Stéphanie, Doctorate in Life and Health Sciences, — 7 min read

IP, SPF and FPS; what do these acronyms mean?

The terms IP, SPF and FPS can be confusing. Some consumers are confused by the sheer volume of sunscreens available on the market, and often end up choosing one at random without worrying too much about the terms displayed on the packaging. In reality, there is no difference at all between the acronyms IP, SPF or FPS. These terms mean exactly the same thing: FPS is the abbreviation for “Facteur de Protection Solaire”, SPF means “Sunburn Protection Factor” and IP is the abbreviation for “Indice de Protection”. The number written on the packaging has the same value, regardless of the brand or where you bought it: this means it is a universal value.

Each of these values represent the level of protection/effectiveness of a sun care product against sunburn caused by UVB rays. The most important thing isn’t the letters, but rather the numbers on the packaging. There are four levels of SPF:

  • From 6 to 15 for weak protection

  • From 15 to 25 for medium protection

  • From 30 to 50 for high protection

  • 50+ for very high protection

These protection values are the link between the exposure time required to burn in the sun, with and without sunscreen. If, for example, a person starts turning red after 5 minutes in the sun without protection, using an SPF 50 sunscreen would allow that person to multiply their exposure by 50 times before getting sunburnt (5 minutes x 50 = 250 minutes). This means that they will need, in theory, 250 minutes, or 4 hours and 10 minutes, to get sunburnt after applying sunscreen.

However, these estimations present a few issues. Certain factors can weaken or even totally eliminate the sunscreen’s effect, like poor application, using insufficient product, sweating, swimming, rubbing with a towel or clothes, etc… Sunscreen is only effective in ideal conditions, which is why you need to reapply regularly to properly protect your skin.

Don’t forget that there are no products which completely block the sun’s rays. The SPF figures tell us the amount of UVB rays that are blocked by your sun care product. That’s why, even when you correctly apply sunscreen, you still tan.

A product which is SPF 15 blocks around 95% of UV rays, SPF 30 protects you against 96.7% UVB, and SPF 50 stops approximately 98.3% UVB.

This means that a sun care product which is SPF 30 absorbs around 97% of UVB rays, and the 3% leftover penetrate your skin.

In other words, the higher the SPF, the better it blocks UV rays and stops them from penetrating your skin, so the better you are protected.

How to choose your SPF

Choosing the right sun protection depends on certain criteria:

  • Your phototype: The lighter your skin, the higher protection you need. Dark, matte complexions, which are less vulnerable to UV rays, can do without the maximum protection as long as they are not subjected to prolonged and repeated exposure to the sun.

  • The season: Even in winter, applying sunscreen is still necessary because UV rays pass through the clouds; in fact, on a cloudy day 90% of UV rays still pass through. However, it’s ok to use medium protection.

  • The time of day: The sun’s strength varies throughout the day, so you can use different levels of SPF at different times. In the morning and evening, you can use a medium protection if you’re outside. However, between 11am and 3pm, choose a higher protection, especially in summer: it’s the time when the UVB rays are at their strongest.

  • Your location: People who live in a tropical climate, where the sun shines all year and through most of the day, must take extra precautions in the sun. As well as an SPF 50 sunscreen, it’s best to limit your exposure to the sun.

Sources :

  • DOWDY J. C. & al. Simplified method to substantiate SPF labeling for sunscreen products. Photodermatology, Photoimmunology and Photomedecine (2003).

  • LIM H. W. & al. Sunscreens: An update. American Journal of Clinical Dermatology (2017).


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