The sun: a double-edged sword
Every year, the sun returns with the same promise: a healthy glow, long days, and a longing for the beach. Yet its effect on the skin is not limited to the tan we see in the mirror a few hours later.
Beneath the surface, UV exposure triggers much more subtle biological responses. This is where much of what we call skin ageing takes place.
What UV rays do to the skin
The UV radiation that reaches the skin consists of two main types of waves: UVA (320 to 400 nanometers) and UVB (280 to 320 nanometers). Together, they trigger a whole series of reactions, some immediate, others much more subtle.
Intense exposure can sometimes cause redness, a burning sensation, or skin that feels tight and quickly loses its comfort. Yet what we feel only tells part of the story.
Inside the tissues, UV rays can directly alter the DNA of skin cells, notably by abnormally bonding two adjacent bases together: what is known as a thymine dimer. This type of damage can also weaken p53, a gene normally responsible for repairing or eliminating damaged cells.
UV rays also increase the production of free radicals. To visualise them, you can imagine tiny sparks: they occur naturally during the body's normal functioning and are not, in themselves, abnormal. The skin also has its own antioxidant systems to maintain balance.
However, when their production becomes excessive, these defences can be overwhelmed: this imbalance is what we call oxidative stress. The sun does not act alone; pollution, smoking and other environmental factors also contribute to this pressure.
Why repeated exposure accelerates skin ageing
A sunburn is visible and can be felt. Skin ageing, on the other hand, sets in quietly, with repeated exposure.
Enzymes that actively break down collagen
Collagen and elastin are not only passively damaged by oxidative stress. UV rays also activate enzymes native to the skin, matrix metalloproteinases, whose role is literally to cut up existing collagen and elastin fibres. Repeated over the years, this enzymatic activity gradually leaves the skin less firm and less elastic: this is what we call photoageing.
A weakened immune defence
The skin contains immune cells, Langerhans cells, which help repair and defend it. Repeated UV exposure can reduce their number and activity, weakening the skin's ability to react effectively to subsequent stressors.
Reduced moisture retention
UV exposure can also weaken the skin's ability to retain water. A weakened skin barrier allows more moisture to escape, resulting in skin that feels tighter more easily and takes longer to regain its comfort.
You could compare the skin to a sail at sea. A gentle breeze sets it in motion. A strong, repeated wind eventually pulls on its fibres. The same is true with the sun: repetition and intensity of exposure are what matter.
How the skin defends itself, and where research is focused
In the face of this pressure, the skin is not defenseless. It has its own antioxidant defences, capable of neutralising some free radicals before they cause damage.
Part of the research in skin nutrition focuses on this area: several antioxidants, obtained through diet or supplements, are being studied for their ability to support this balance against the sun. Astaxanthin, a carotenoid of marine origin, is one of them: its structure allows it, among other things, to interact with the lipid environment of cell membranes, which is directly affected by oxidative stress.
These nutritional approaches remain a support, never a substitute: none of them blocks UV rays at the source.
The daily habits that matter
Reducing the sun's impact on the skin is less about a single action than about a set of consistent habits.
Protection as the first line of defence
An appropriate SPF, shade, protective clothing, sunglasses, and limiting the most intense exposure: these are the actions that directly reduce the amount of UV rays reaching the skin. Nothing can replace them.
What supports the skin daily
Alongside this protection, other habits matter: a varied diet rich in colourful plant foods, sufficient hydration, and skincare that preserves the comfort of the skin barrier. Their consistency matters more than their occasional intensity.
Looking beyond the tan
The sun does not only act on the surface. Behind the tan, invisible mechanisms are set in motion, accumulating with repeated exposure to gradually create the bulk of sun-related skin ageing.
Understanding what really happens in the skin allows you to approach summer differently: less as a race to get a tan, and more as a season to prepare for with the right habits.
Are you wondering which antioxidants are being studied to support the skin against this pressure? We have dedicated a full article to one of them, astaxanthin: discover our article on astaxanthin.