What effects do the sun's rays have on skin?
The sun's rays have an undeniable effect on both mood and well-being. Sunlight effectively runs the show by stimulating the production of essential hormones that regulate the body's biological rhythm. This influences your sleeping pattern and also affects your mood.
The sun's warmth and light «enhances your general feeling of well-being and stimulates blood circulation,» according to the World Health Organization.
The sun's rays can disrupt the functioning of key natural defenses in the body when they are absorbed by the skin.
The potential damage caused by UV light is partly down to its ability to cause breakages in cells' DNA. These cells must repair the damage but may make mistakes and mutate, which increases the risk of developing cancer. A distinction must be made between «non-melanocytic» cancers and melanomas.
The first type of cancer develops more slowly and is less likely to be fatal. Surgical treatment can be painful and leave scars.
The second type is very dangerous.
Excessive sun exposure during childhood appears to be a more significant risk factor than exposure later in life.
Ultraviolet rays are necessary for vitamin D synthesis. These are called B (UVB) rays and enable the production of vitamin D using a cholesterol derivative that is found naturally in skin.
UV rays trigger several different reactions on contact with the epidermis. They generally cause a sun allergy, where the slightest sun exposure leads to a skin eruption or severe sunburn. There are also cases of photo-induced toxicity as a result of taking certain types of medication (non-steroidal anti-inflammatories, analgesics, antibiotics or antidepressants).
This is the most visible reaction to UV light: skin turns brown when exposed to the sun.
UV rays affect two types of cells:
- Keratinocytes: these are the predominant cells in the skin and multiply to form thick layers, offering better protection.
- Melanocytes: these cells are found in the skin's deepest layers and produce melanin under the action of UV rays. This protective brown pigment is responsible for tanning skin.
Be careful! Melanocytes can't produce melanin all day long. Prolonging sun exposure will not make your skin more tanned. On the contrary, this runs the risk of having the opposite effect, leading to sunburn or damage to other structures in the skin. UV radiation stops being neutralized in the skin once melanocytes and keratinocytes are "saturated".
UVA and UVB are responsible for the skin's aging.
UVA rays penetrate the deepest layers of the epidermis, altering the elastic fibers and collagen which form part of the structure of the dermis. Skin loses its natural elasticity through the breakdown of the connective tissue. The neck, face and hands suffer the most from over-exposure to UV rays.
Loss of elasticity in the skin encourages the appearance of wrinkles. Sun exposure without using sun protection leads to sun spots on the face that never go away.
What happens when the skin burns?
The skin always reacts in the same way during sun exposure. It deepens in color to protect itself against UV rays, which attack the epidermis and dermis. This is sunburn.
This is tanning. Its natural defenses are effective but also limited. The skin burns when it can no longer defend itself against the amount of UV radiation it is exposed to. This affects the deep tissues and causes skin to become red and painful.
The skin may receive the maximum dose of UV it can tolerate very rapidly. Depending on the individual, just 30 minutes in the midday sun can be enough to ""catch"" the sun.
Why protect the skin?
Sunburn does not strengthen the skin and will not make it more resistant to the sun. On the contrary, it weakens the skin's resistance to the sun and increases the risk of irreparable damage. So much so that suffering from excessive sunburn as a child is a risk factor for skin cancer in adults. The accumulated dose of UV radiation during your lifetime is therefore a major factor. Skin won't tan evenly anymore after this capital has been exhausted, and dark spots become more frequent.
Do sun care products prevent tanning?
Sun cream was invented specifically to stop skin reaching its breaking point. It acts as a protective barrier between skin and the sun:
By reducing the quantity of UV radiation absorbed by the skin, it allows melanogenesis (tanning) to take place under the right conditions.
What does SPF mean?
Sun Protection Factor is an index used to indicate the product's capacity to protect the skin. SPF is related to skin sensitivity. More sensitive skin requires sun care products with a higher SPF.
What is the difference between UVA and UVB?
A small quantity of UVB radiation passes through the atmosphere (just 5%). Despite the earth's significant filtering effect, this amount is generally enough to trigger the synthesis of vitamin D on contact with the skin. It also causes tanning and, in excess, sunburn
These rays can also reduce the skin's immune defenses. Repeated UVB exposure over the long term has an impact on the structure and integrity of the epidermis. These rays contribute to the skin's aging and the appearance of some types of skin cancer.
Most UVA rays are not filtered out by the atmosphere. They travel directly from the sun to our skin and penetrate more deeply than UVB rays. UVA travels through the epidermis and boosts the synthesis of melanin, which causes tanning. However, it mainly targets the skin's elastic fibers. This means UVA rays are the main cause of photo-aging. The effects of UVA on skin are not limited to aging. They also appear to form lesions in the cells' DNA, which encourages the development of skin cancer.
How do you choose a cream and how much should you use?
Choose according to your skin type:
Use very high protection on your face and neckline if you are pregnant during the summer: SPF 50+.
If you don't use sun protection when you are pregnant, you have a greater risk of getting brown spots known as melasma on your face and neckline.
Skin with low sensitivity to the sun:
You only need to use very high protection (SPF 50+) in extreme conditions, like the tropics, high altitudes and glaciers. Use high protection (SPF 40) for the beach and medium protection for daily activities when you are not particularly exposed to the sun (SPF 20).
Sun-sensitive skin that burns easily:
You should use SPF 50+ religiously at all times (beach, playing games in the park etc.)
These skin types have better resistance against UV rays and sunburn is less of a concern. Medium protection (SPF 20-40) is enough to protect your skin against sun damage.
Skin that never tans but looks sunkissed:
Products with high protection are the safest bet for those who often burn in the sun. Use SPF 30 to 50+ for the beach or for prolonged exposure.
It doesn't matter if babies' skin is light or dark, children under 3 should never be directly exposed to the sun! Your baby's skin is very fragile and you should protect it from indirect sunlight (in the pushchair or underneath a parasol) using very high factor sun cream with an adapted formula (fragrance and paraben-free).
Choose according to product type:
To benefit from the level of protection advertised, apply the right amount of sun care product.
- - tube, use a finger width of product for the whole face.
For the body:
- - tube: Apply two finger widths of cream. This is the standard amount needed for each arm, leg (back and front), upper back, lower back, chest and stomach.
- spray bottle: the equivalent of 6 sprays on the forearms of an adult.
Self-tanning products don't protect you from the sun.
A self-tanning product can never be used instead of sun protection. It is designed to give skin an artificial tan and does not contain any UV filters.
UV intensity reaches its peak between 11 am and 3 pm.
When the sun is at its zenith, UVB rays travel through the Earth's natural barriers more easily. More radiation gets through these filters and has a higher energy capital by the time it reaches us than at other times of day. This makes it more dangerous and harmful for the epidermis.
Over-exposure to the sun accelerates the skin's aging.
UV rays can cause brown spots, but they also contribute to wrinkles.
I don't need to use sun protection when it's cloudy.
The sun continues to emit UV rays behind the clouds. Low cloud coverage provides a good barrier against UV but that's all. If clouds are higher in the sky, they provide less protection against rays which can burn and damage the epidermis more deeply.
The sun encourages vitamin D synthesis.
In fact, the sun's rays themselves play a part in the production of vitamin D. The inactive pro-hormone stored in the skin transforms into active vitamin D under their influence.
The sun is strongest in the tropics.
The sun is strongest in the tropics because its rays shine vertically. Vertical rays are not "stronger" in the tropics, but travel through thinner atmospheric layers and are therefore less absorbed by the atmosphere.
The sun is more dangerous on mountains.
Dry sand reflects 15% of the sun's rays on impact and the foam on waves reflects around 25%. Contrary to what you might think, the sun's rays are much stronger on snow-covered mountains as the snow reflects between 75% and 90% of UV rays.
You should also take the altitude into account when you are on a mountain. This contributes to the intensity of the sun's rays which increases by 4% every 100m.