Sun and Skin: Understanding what is happening at the heart of your epidermis

27/05/2024

Soleil et Peau : Comprendre ce qu’il se passe au cœur de votre épiderme

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Camille A.

It beautifies our life and our complexion, warms us, and is essential to our well-being. However, it should be consumed in moderation. It's about the sun! And the first to suffer the damage is our skin.

If you want to know more about skin pigmentation, photo aging, but also about the benefits and harmful effects of the sun, this article has been written for you.

1. Solar radiation

The sun emits 3 types of radiation, each characterized by their length:

IR, infrared rays

With wavelengths between 700 and 2,000 nm, it is to these rays that we owe the sensation of heat from the sun.
The visible rays

With a wavelength between 400 and 800 nm, visible rays allow us to see the world in color. Blue, green, red... our eye is capable of seeing these rays.
UV, Ultraviolet rays

With a wavelength between 100 and 400 nm, these are the most energetic rays in the solar spectrum. UV rays cause the most damage to our skin and are particularly responsible for its accelerated aging.

Let's focus on UV rays:

UV rays themselves are broken down into 3 rays reaching our skin more or less deeply¹ :

UVA

UVA rays penetrate the skin to the dermis. More precisely, 80% of UVA rays pass through the epidermis and 20% reach the dermis.

UVB

UVB is blocked by 70% by the stratum corneum and its components (keratin and melanin) on the surface of our skin. Only 20% of UVB rays reach the deep epidermis, and less than 10% reach the dermis.

UVC

UVC does not impact our skin because it is absorbed by the ozone layer. They therefore do not penetrate our atmosphere and do not reach the Earth's surface.

Did you know ?

We are not all subject to the same solar radiation depending on our geographic location and our environment. Several criteria come into play:

Latitude : an inhabitant of the North Pole is subject to less aggressive radiation than an inhabitant close to the equator.
Altitude : at high altitude, we are more vulnerable because the atmosphere absorbs less rays. It is estimated that the intensity of solar radiation increases by 10% for every 1000 m of altitude difference.
The environment : depending on the landscape around us, the reflection of the sun's rays on surrounding surfaces is more or less intense. A light surface reflects a lot of solar radiation. Snow reflects 85% of the sun's rays, the sea 25%, sand 15% and grass and soil less than 10%.
Clouds : dense cloud cover reduces our exposure to the sun.

Source: https://www.who.int/fr/news-room/questions-and-answers/item/ultraviolet-(uv)-radiation

2. Skin pigmentation

The skin pigmentation process:

The natural color of our skin is determined, genetically, by its pigmentation. This is based on the activity of specific cells of the epidermis, the melanocytes, at the origin of the synthesis of the skin pigment: melanin.

Although all skin has the same number of melanocytes, each skin tone is characterized by a variable quantity of melanin and different types of melanin produced by the epidermis. What we commonly call melanin is, in reality, a mixture of several pigments:

Eumelanins: these melanins are dark in color, brown or black, and present in large quantities in dark and olive skin.
Pheomelanins: yellow-red in color, these pigments are more characteristic of light skin (and particularly red skin).
Each individual has these different melanins in varying proportions.

Once produced by melanocytes, melanin diffuses into the layers of the epidermis. With cell renewal, it reaches the surface of our skin and gives it its natural tone.

The photos:

Our skin color, or complexion, determines our phototype. There are 6 distinct phototypes used to classify skin colors according to their physical characteristics (skin tone, eye and hair colors) and their sensitivity to the sun. If you have fair skin, you certainly know that your skin's sensitivity to the sun is greater than that of dark skin.

3. Les effets du soleil sur notre peau

Ami ou ennemi, le soleil joue sur les deux tableaux. Si ses rayons nous procurent certains bienfaits bien appréciables, il possède cependant des effets dont il faut se protéger. A consommer avec modération donc !

Les effets bénéfiques du soleil :

Bronzage et effet bonne mine :

On aime surtout le soleil pour le joli hâle qu’il nous donne, ainsi que pour son action bronzante. En atteignant notre peau, les UV activent son mécanisme de pigmentation. Dans ce processus naturel, les UV stimulent les mélanocytes, les cellules de l’épiderme en charge de la production de mélanine, le pigment de la peau. Ainsi, sous l’effet des UV, notre peau augmente sa production de mélanine. Celle-ci se dissémine ensuite dans l’ensemble de l’épiderme, et notre peau se colore.

Comprendre la pigmentation :

Deux phénomènes¹ se produisent lorsque notre peau est exposée aux UV :

La pigmentation immédiate : apparaît rapidement et ne perdure que quelques heures après l’exposition. C’est elle qui donne à notre teint un joli hâle. Il s’agit d’une réaction de photo-oxydation de la mélanine déjà présente dans l’épiderme sous l’effet des UVA.
Bronzage, ou pigmentation retardée : ici, ce sont majoritairement les UVB qui activent la synthèse de mélanine nouvelle. La coloration de la peau apparaît entre 2 et 3 jours après l’exposition, et atteint son maximum en moyenne en 3 semaines.

Qu’elle soit immédiate ou retardée, la pigmentation est avant tout un mécanisme de défense de la peau pour se protéger des effets néfastes des UV. En présence d’UV, la mélanine absorbe le rayonnement UV pour éviter qu’il n’endommage d’autres composés (ou organites) cellulaires.

The synthesis of vitamin D:

It is thanks to the sun that our body knows how to synthesize vitamin D, a very valuable vitamin for our skeleton and the maintenance of normal bones and teeth, but also for our immunity and effective natural defenses.

A short exposure to the sun is sufficient to meet our vitamin D² needs: simply expose your forearms and face for between 5 and 10 minutes, two to three times a week.

FEMME-AVEC-SA-FILLE-ET-SA-MERE-SUR-LA-PLAGE

A positive effect on morale:

You've probably already felt it, the sun boosts our morale. And the feeling of well-being it gives us doesn't just come from its gentle warmth. It is proven that sunlight impacts the production of serotonin, the feel-good hormone, involved in many functions such as the sleep-wake cycle, mood, anxiety, and even pain. When the days get shorter and the ambient light is low, serotonin production drops, bringing with it a drop in our morale. This is why our morale is better in summer.

If the sun presents some significant benefits for our well-being, we must nevertheless be aware of its harmful effects which weigh heavily in the balance. Here's why the sun isn't just a friend.

Les effets néfastes du soleil

L'allergie au soleil

Aussi appelée lucite estivale, l’allergie au soleil survient généralement après les toutes premières expositions de la peau au soleil. L’allergie au soleil se manifeste par l’apparition de petits boutons ou de papules plus importantes, avec une forte envie de se gratter. Elle peut persister quelques jours et finit par s’estomper pour ne plus réapparaître au fil des expositions répétées.

Sunburn or solar erythema

Sunburn appears after prolonged and high intensity exposure of the skin to UV rays. This is a skin burn mainly caused by UVB (and to a lesser extent by UVA). Fair skin is even more prone to it. Solar erythema can affect the skin with 4 degrees of intensity ³ , from a simple pinkish coloring of the skin, to the appearance of pain and intense burning sensations, edema, or even blisters (blisters) filled with liquid. Sunburns also cause more or less significant peeling of the skin. The risk of “getting a sunburn” is all the greater the lighter the phototype.

Dehydration of the skin

You have probably already noticed that your tanned skin is often dehydrated. Skin hydration is based on several parameters including the presence of lipids in the lipid cement between the cells of the epidermis. UV rays are responsible for the oxidation of these lipids. Degraded, they can no longer effectively play their role as cement and allow water to evaporate, thus leading to dehydration of the skin.
The appearance of spots

UV rays trigger the production of melanin. Over time, this natural process becomes less efficient, becomes disrupted and leads to the appearance of pigment spots, or solar lentigos.
Melasma is another form of skin hyperpigmentation induced by the combination of sunlight and the female sex hormones estrogen and progesterone. Melasma mainly affects women, including pregnant women and those on contraception, and occurs over large areas of the face.
Acne and the rebound effect

If during exposure to the sun, acne seems to improve, this is without taking into account the rebound effect which generally occurs once exposure is over. Indeed, at first glance, the sun has a drying effect favorable to oily and acne-prone skin. However, when the exposure stops, the epidermis has thickened, which prevents the proper natural flow of sebum through the pores. This obstruction then promotes the retention of sebum in the skin and the inflammatory lesions characteristic of acne.

Photoaging

Also called helioderma, photoaging is the aging of the skin induced by chronic exposure to the sun. It mainly affects photoexposed areas such as the face, forearms, neckline, and hands.
Photoaging results from several phenomena induced by UV ⁴ :

the degradation of cells of the dermis and epidermis,
the massive production of free radicals causing significant oxidative stress,
activation of the inflammatory response,
alteration of collagen fibers and elastic fibers.

At the clinical level, this results in more marked signs of aging: deepening of wrinkles, loss of elasticity, sagging and loss of firmness, loss of skin density and the appearance of spots.

Skin cancers

The sun is classified as a carcinogenic factor by the IARC (International Agency for Research on Cancer). More than 80 % of skin cancers are caused by overexposure to UV rays. Skin cancers develop over the long term and result from UV-induced mutations in our genes. Exposures in childhood and adolescence are decisive in the occurrence of cancers in adulthood.

In order to prevent the risk of skin cancer, it is recommended to avoid as much as possible (or limit when it is not possible to avoid) exposure to the sun, and above all, to protect yourself effectively. with sun protection containing filters.

At the slightest change in your skin, it is then essential to intervene as early as possible, it is essential to be attentive: if a new brown spot appears or if a mole seems to be changing, do not hesitate to consult a dermatologist for a precise examination.

Les formules TOPICREM ont toutes été conçues dans le but d’apporter une hydratation protectrice et préserver la barrière cutanée des peaux sensibles de toute la famille.

Pour cela, notre laboratoire s’appuie sur son expertise issue de l’excellence pharmaceutique :

Sélection d’ingrédients haute tolérance à l’efficacité prouvée,
Développement de formules cliniquement testées sur peaux sensibles,
Efficacité démontrée par la science et approuvée par les consommateurs.

Par le confort et le bien-être émotionnel qu’ils procurent, nos soins vous aident à vous sentir en confiance avec votre peau et avec vous-même, à mieux vous révéler aux autres, et ainsi à profiter pleinement de chaque moment de la vie.

¹ Mélissopoulos A, Levacher C. The skin, structure and physiology, 2nd edition. Lavoisier.2012.

² Weekly epidemiological bulletin, May 22, 2012/ n°18-19, National Health Monitoring Institute available at: http://www.invs.sante.fr/fr/content/download/36751/177365/version/3/file /beh_18_19_201 2.pdf

³ Warrick E. Tissue effects of UV [Internet]. https://biologiedelapeau.fr. 2014. Available at: https://biologiedelapeau.fr/spip.php?article74

⁴ Leccia MT. Photo-induced skin aging. EMC - Cosmetology and aesthetic dermatology. Jan 2006;1(1):1-10.

⁵ https://www.worldwidecancerresearch.org/