Podcast: Episode 31, 5 tips for sunscreen experts

Listen to the audio episode to become an expert on your sunscreen

Best practices with your SPF:

  • Apply an amount of sunscreen equivalent to two lines of the length of the fingers on the face.
  • Choose a texture of sunscreen that you apply and reapply in sufficient quantity.
  • Avoid spray or mist sunscreen products, as it is difficult to apply enough of them.
  • Use sun protection if the sun hits your skin directly through a window (car).
  • Combine your sunscreen product with antioxidant-rich skincare products.


The sun attacks the skin daily and accelerates the appearance of the signs of aging, including wrinkles, fine lines and loss of firmness. All the protections that would limit the damage linked to the sun are good to take: clothes, wide-brimmed hat, glasses, sunscreen... but do you know how to use the latter? How much product used ? What product used?


The skin is not a completely flat surface, it has micro-reliefs with hollows and bumps. The amount of sunscreen product applied must therefore be sufficient to fill in the hollows and cover the bumps, for uniform protection.

The more sunscreen you apply, the better the protection.

The SPF is calculated on human volunteers by applying a quantity of 2 mg of product per cm² of skin¹ . It is difficult to imagine this quantity, so let's take a very concrete example: the skin of an adult represents ~ 1.8 or 18,000 cm² . To apply 2 mg/cm² all over the body, you would have to apply 2 x 18,000 mg = 36,000 mg of cream, i.e. 36 g of cream per application on the body. That's a fifth of your 200 mL sunscreen! At this rate, your sunscreen is only 5 uses.

Rest assured, the amount used in SPF testing does not imply that consumers should apply the same amount. The amount was determined by experiment to be the lowest amount giving reproducible results³ .

That said, you can't be too protected, any protection is good to take. So if you want to benefit from the SPF indicated on the bottle of your sunscreen, for use on the face, you must put about 2 mg/ cm² x 565 cm² = 1130 mg = 1.13 g of sunscreen on the face . The surface of the face for the application of cosmetics has been evaluated at 565 cm² by a study reused in the reports of the SCCS, Scientific Committee for Consumer Safety. An easy way to approximate these 1.13 g is to draw 2 lines of sunscreen the size of your index and middle finger.

best sunscreen 2022

In 2007, a study determined the sun protection actually obtained according to the amount of sunscreen applied, on human volunteers. The relationship would be exponential, i.e. the application of 1 mg/ cm² (half the dose used for the SPF calculation), would result in sun protection equal to the square root of the claimed SPF, not half the claimed SPF. This study remains to be put into perspective, because it was carried out with an SPF 4, and I am not sure that we would obtain the same results with an SPF 30.


I advise you to choose a sunscreen product with a minimum SPF 30 (50 if your skin is fair or during the summer) and bearing the circled UVA logo or the mention broad spectrum. This will allow you to have good protection against UVB and UVA.

✅ SPF 30+

Regarding the texture, I advise you to choose a texture that you like to apply and reapply in sufficient quantity . Personally, I do not use sun oils for the face because I usually apply only a few drops to limit the oily and shiny finish. With this amount, my skin is not sufficiently protected from the sun. I advise against relying solely on your foundation, BB cream or any other tinted product, because you generally apply less of it than a cream. I also advise against SPF powders, which are found in particular in the USA, because 2 mg of powder does not hold and is not absorbed by 1 cm² of skin.

✅ Texture easy to apply in large quantities
❌ Make-up with SPF

Next, don't be fooled by the product name when it comes to moisturizers with an SPF or sunscreens with the same SPF . This is only a marketing decision, because the tests carried out are identical. The only differences may be price and other assets.

✅ Moisturizer with SPF = Sunscreen

When it comes to packaging, I don't recommend mists, sprays, or sprays (although they're particularly nice) because you don't apply enough product with these delivery systems.

❌ Mist, spray, sprayer

Overall, a product with the highest SPF, whose texture you like, and that you like to apply daily and reapply, that corresponds to your budget and your ethical and environmental values: this is what you need!


The answer is not universal, as it depends on exposure conditions, your phototype and risk/family history.

When I take the car, I apply sunscreen, because UVA rays pass through the windows. In addition, we are near car windows and the sun's rays can hit our skin directly.

In a windowless room, or in the basement, I certainly wouldn't take the time to apply it.

Inside, we are exposed to diffuse radiation, because we are not directly exposed to the sun. The further you are from the window, the less you are exposed to UV. Similarly, the less we see the sky from our window (trees, buildings, etc.), the less we are exposed to UV. What does this represent concretely?

By being 1 m from our window, the surface of the window corresponds to 17%⁵ of our surroundings (estimating our surroundings as a dome around us). So at 1 m from a window through which we see only 50% of the sky, because the view is cluttered by trees, buildings, we recover that 17/2 = 8.5% of diffuse UV, which themselves are a portion of all UV. The need to wear a sunscreen is then reduced.

If skin pigmentation, the appearance of wrinkles were one of my biggest fears, or if I had a family history of skin cancer, I would wear sunscreen daily, regardless of my environment.

It is not recommended to wear sunscreen if the maximum UV index for the day is 1 or 2 . As a reminder, you can find this information on your phone's weather app. It depends on your phototype and therefore your ability to protect yourself from UV rays naturally. The majority of studies are done on white skin so there is a certain bias regarding the recommendations to wear an SPF.

Knowing that black skin can have natural protection equivalent to white skin wearing an SPF 50 ³ , we quickly understand the limits of generalized recommendations.


Tanning is a defense reaction of the skin against the stress that the sun causes it. It is an adaptation in the face of an aggressor. Tanning can allow white skin to achieve natural sun protection equivalent to their non-tanned skin wearing a product with an SPF 10³ .

However, I would not voluntarily expose myself to UV cabins which attack my skin, in anticipation of a trip with particularly significant sun exposure.


Sun filters are listed in appendix VI of European cosmetic regulation 1223/2009. This appendix contains less than thirty sunscreens. There are actives called " boosters " which are not listed in the regulations, but which help to achieve high SPF.

Antioxidants also help scavenge UV-caused free radicals in the skin. Thus, they neutralize free radicals before they damage components of the skin. Antioxidants are always good for the skin, morning and evening, unlike sunscreens which are recommended only during the day. That's why I wanted to include a lot of antioxidants in Mastel skincare so that they help slow down the appearance of the signs of aging in the morning and evening. The Cream - Moisturizes and Beautifies Age contains powerful antioxidants: Ginkgo biloba and Coenzyme Q 10.

Mastel's GINKGO SACRÉ Cream is your ally to moisturize and beautify age . It contains French Ginkgo biloba obtained by cell cultures to slow the appearance of signs of aging.

The duo, antioxidant and SPF are real BFFs (Best Friends Forever): they work really well together to slow down the appearance of the signs of aging.

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best sunscreen 2022
best sunscreen 2022
best sunscreen 2022


¹ISO _ . ISO 24444:2019 Cosmetics — Sun protection test methods — In vivo determination of sun protection factor (SPF) . 2019 . Available at: https://www.iso.org/obp/ui/#iso:std:iso:24444:ed-2:v1:fr

²Scientific Committee on Consumer Safety. ADDENDUM to the Opinion SCCS/1506/13 On Climbazole . 2013. Available at: https://ec.europa.eu/health/scientific_committees/consumer_safety/docs/sccs_o_120.pdf

³ THINK-LHERITIER AM. Design of cosmetic products: Formulation . 2016. Lavoisier, Paris.
⁴ FAURSCHOU, A. and WULF, H. The relationship between sun protection factor and amount of suncreen applied in vivo . 2007. British Journal of Dermatology. Available at: https://doi.org/10.1111/j.1365-2133.2006.07684.x
⁵ WONG, Mr. Should You Wear Sunscreen Indoors? The Science (with video) . 2020. Available at: https://labmuffin.com/should-you-wear-sunscreen-indoors-an-analysis-with-video/#more-10720
⁶ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY. UV Index Scale . 2022. Available at: https://www.epa.gov/sunsafety/uv-index-scale-0

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A chemist in the cosmetics industry for more than 5 years and a graduate of the Natural Raw Materials in Cosmetics Master's degree from ISIPCA, Julie is an expert in the development of natural cosmetic products.