The effectiveness of some sunscreens would be greatly overestimated

The effectiveness of some sunscreens would be greatly overestimated

Essential for summer holidays, sunscreens are essential to protect against ultraviolet rays. But the analysis of 14 of them by two researchers from Nantes calls into question their effectiveness. We explain to you.

In the newspaper The Parisian on August 15, Laurence Coiffard, professor of pharmacy, and her fellow researcher Céline Couteau shared the results of their annual research on the effectiveness of several sunscreens. Their objective is to verify that the protection index (more precisely 50 or 50 +) displayed on the sunscreen products corresponds to what is indicated.

A-Derma Protect 50 + sun products in the crosshairs

As our colleagues point out, this year, the two researchers decided to analyze fourteen sunscreens (in spray or stick) and the result of the analyzes carried out in their laboratory at the University of Nantes is not very glorious.

Result: only 55% of the products “tell the truth”, with an “efficiency at the height announced”. According to the results collected in their laboratory at the University of Nantes, the scientists have shown that a solar stick promising an index UV 50 was finally evaluated at… 34. A cream obtained a result of 20 and a solar fluid only 12. Even more worrying, a product claiming to be “suitable for infants” would actually have an index of 3.7!

“For a cream to protect, UV filters must be added to the basic ingredients. The more we put, the higher the index, it is a real technical operation, deciphers the specialist. However, we see everything and anything on the shelves. Products with so-called mineral filters are not better, but even worse: labeled organic or not, none have proven effective up to a real index of 50 or 50 +”explains the researchers for Le Parisien.

Avoid sunscreens containing alcohol or perfumes

For Laurence Coiffard, sunscreen is the form of sun protection that offers the most effective protection. But for that : “It must be white, opaque, without perfume or embellishment. In other words, sober”. The latter must therefore not contain alcohol or perfume. “When I see alcohol or perfume in the composition, it makes me jump, it’s totally unacceptable. They have allergenic, even photoallergic effects”, alarms the professor of pharmacy to our colleagues.

For this researcher, the results of her anamlysis are important as skin cancers explode with a number of cases having tripled between 1990 and 2023, according to the National Cancer Institute (INCa).

However, for the scientific adviser to the Federation of Beauty Companies (Febea), Erwan Poivet, these products incriminated in the research of the two Nantes residents comply with the international standards imposed. “The sunglasses found on the market, whether small or large brands, are safe and controlled. It is in the interest of no manufacturer to misrepresent. Their product meets the internationally recognized ISO 24444 standard. You don’t buy anything”he defends with our colleagues.

A different method of analysis

For their analysis, the researchers used a different method than the one used to calculate the protection index. Generally, the tests are carried out “in vivo on human guinea pigs on which UV light is directed to calculate the time of onset of sunburn”, explain The Parisian. They then used an in vivo method in the laboratory, using a rough plate that mimics the surface of human skin. To do this, they applied the sunscreen product, then “pass it all in a robot-like device that calculates the amount of UV able to pass through the plate”.

“I don’t think that manufacturers lie shamelessly. The problem is the method. That of the Nantes researchers is necessarily more reliable than in vivo, which does not mimic real life conditions”, says Professor Christophe Bedane for The Parisian. He then explains that “to meet the set criteria, the product should be applied at a rate of 2 mg/cm2 of skin. In fact, we apply about a quarter of this quantity, and 50 to 70% for children” .

“The Phalanx Unit”

In order to properly apply his sunscreen, Pr Christophe Bedane shared a simple and effective tip with our colleagues at The Parisian“the phalanx unit”.

First, you just need to take the first knuckle of your thumb. Then apply cream along the entire length to make a “little pile”. The number of phalanges varies according to the area of ​​the body:

  • Three knuckles for the face;
  • Four phalanges for each arm;
  • Eight phalanges for each leg;
  • Nine to ten knuckles for the back and torso.

As a reminder, don’t forget to apply sunscreen to your body every two hours and after swimming. Also avoid exposing yourself between 12 p.m. and 4 p.m. These are the times when UV rays are most intense and therefore the most harmful to your health.

Experts also point out that “Do it yourself” sun protection, that is to say, do it yourself at home, does not offer any protection. Just like the recent TikTok trend for getting a tan quickly: “Beer Tanning”, which consists of coating your body with beer before sunbathing.