In our quest for healthy, protected skin, it's crucial to understand the radiation emitted by the sun and its impact on our epidermis. Let's take a look at the different shades of these rays and their implications for skin health.
The sun emits a broad spectrum of radiation, including both visible and UV light. The term " UV " stands for " ultraviolet ". Violet is the color with the highest frequency of visible light. Ultraviolet is therefore radiation "beyond" violet that is invisible to the human eye.
UV rays are classified into several categories according to their wavelength. UVA extends from 315 to 400 nm, UVB from 280 to 315 nm and UVC (stopped by the ozone layer) from 100 to 280 nm.
High-dose exposure to UVA and UVB rays is harmful to our health and our skin.
The WHO estimates that " more than 90% of the global burden of melanoma and other skin cancers is attributable to exposure to
UV radiation". UV rays have no effect on the sensation of warmth we feel in the sun, which is due to infrared rays. It's important to note that UV rays are all around us, even on cloudy or cold days!
That's why we need to protect our skin from the sun, whatever the weather.
Beware of preconceived ideas: SPF 50 does not mean that the product will protect you for 50 minutes!
The SPF (Sun Protection Factor) is the ratio between the minimum erythemal dose (the smallest amount of UV rays that triggers sunburn) on skin protected by a sun protection product and the minimum erythemal dose on the same unprotected skin.
The SPF is a ratio of time with and without sun protection before sunburn. In other words, it takes 50 times longer to sunburn with SPF50 sunscreen than without. Note that an SPF 30 product blocks 96. 7% of UVB rays, while an SPF 50+ blocks 98. 3% of UVB rays.
UVB = Burn = Immediate effect
UVB represents 5% of all UV and is responsible for the tan seen 48 to 72 hours after exposure. It has long been proven that they induce DNA lesions (deleterious DNA damage) and promote the development of skin cancers.
Sunburn is a visible symptom of UVB overexposure. It is a skin burn that can be first-degree (redness
without blistering), second-degree (blistering)
or deep second-degree (destroyed skin vessels).
UVA = Age = Long-term effect
Historically, harmful effects were attributed solely to UVB. It has been shown that UVA also plays an important role in DNA damage, inducing photodermatoses (abnormal skin conditions (redness, blistering, etc.) following exposure to the sun) and photoimmunosuppression (the pathogenic consequences of UVB radiation can be seen in the aggravation of infectious diseases and the development of skin cancer).
UVA radiation is also involved in skin ageing. It accounts for 95% of UV rays and damages elastin and collagen fibers in the dermis, promoting skin slackening and the appearance of signs of aging.
William Edward McElligott, a 59-year-old American, is a perfect example of this
phenomenon. The left half of his face looks aged, with deeper wrinkles and sagging skin. William Edward is a delivery driver who spends most of his day
in his truck. UVA rays passing through the glass have induced photoaging on the exposed part of his face.
It is therefore very important for a suncare product to be broad-spectrum
(i.e. to protect against UVB and UVA rays), so that the user is sufficiently protected against the harmful effects of the full UV spectrum of
solar radiation.
The WHO states that applying a broad-spectrum sunscreen with a protection factor of at least SPF15 is one of the safety measures that couldprevent a large number of cancers caused by UV radiation.
Protecting your skin from UV rays, whether it's sunny or cloudy, is vital to prevent long-term damage. Choose a sun protection for complete defense against the sun's harmful effects, and adopt safe practices for your outdoor activities.