In 2012, the New England Journal of Medicine published a photograph of a 69-year-old American truck driver. He had driven for twenty-eight years, with the window on his left. The left side of his face was deeply marked, thickened, and furrowed with deep wrinkles. The right side looked like that of a much younger man.
Same person, same genes, same age, same habits. The only variable was the sunlight coming through a car window. It is the clearest demonstration there is of something that changes everything: skin aging is not just one thing. It consists of two different processes that occur together, and we can do something about only one of them.
Article written by Elisa Avalle, founder of LeLang Skin Care and a dermocosmetics specialist. Cover image generated with the support of artificial intelligence.
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The two speeds: intrinsic and extrinsic
Intrinsic, or chronological, aging is written into biology. Fibroblasts slow down, cell turnover takes longer, and the production of lipids and hyaluronic acid declines. It progresses slowly and fairly uniformly throughout the body. It cannot be stopped, and there is no point in fighting it.
Extrinsic aging is induced by what the skin is exposed to: ultraviolet rays above all, followed by pollution, smoking, stress, sleep deprivation, and diet. Research groups it under the name skin exposome, the collection of cumulative environmental factors we are exposed to over the course of our lives.
The difference is visible to the naked eye, and you don't need to be a truck driver to notice it: compare the skin on the inside of the arm with that on the back of the hand. The same chronological age, completely different exposure.
| Intrinsic | Extrinsic | |
|---|---|---|
| Cause | Time and genetics | Environmental exposure |
| Appearance | Thin skin, fine wrinkles, even complexion | Thickened, leathery skin, deep wrinkles, spots, visible capillaries |
| Where it is visible | The entire body | Face, neck, décolleté, backs of the hands |
| Can it be slowed down? | A little | A lot |
And this is where the good news lies. The part that has the greatest impact on the appearance of the face - spots, deep wrinkles, loss of firmness, uneven complexion - largely belongs to the second group. In other words, the modifiable part.
The five mechanisms that age the skin
Behind the appearance are distinct biological processes. Distinguishing between them matters, because each treatment acts on one or two of them, and none acts on all of them.
1. Oxidative stress
It is the driving force behind almost all the others. UV rays, pollution, and smoke generate free radicals, unstable molecules that damage lipids, proteins, and cellular DNA.
2. Collagen breakdown
Free radicals induce cells to produce metalloproteinases, the enzymes that break down collagen. This is the mechanism through which the sun truly causes aging: it does not burn the fibers, but makes the skin produce the enzymes that break them down.
There is a second change involving collagen that is less noticeable. It is not just the quantity that declines: the type changes. Type III collagen, the most elastic type, progressively decreases, while type I collagen becomes stiffer due to the formation of cross-links promoted by free radicals. The result is a dermis that still has structure but is stiffer and slower to repair.
3. Glycation
Excess sugars bind to structural proteins, forming advanced glycation end products. The result is not less collagen: it is stiffer collagen, which loses its ability to deform and return to its original shape. It is a slow process largely linked to diet, explained in the article on skin glycation.
4. Loss of elastin
Elastin is the protein responsible for elastic recoil, and unlike collagen, the adult body produces very little of it. In skin that has been heavily exposed to the sun, degraded and disorganized elastic fibers accumulate: this is why skin with extensive sun exposure appears thickened and yellowish, not just wrinkled.
5. Low-grade chronic inflammation
A constant, subclinical level of inflammation accelerates all the processes described above. It is caused by pollution, chronic stress through cortisol, and insufficient sleep. This is why a difficult period shows on your face even when your skincare routine remains the same.
The exposome: what really accelerates the process
Ultraviolet rays. The number-one factor, without equal. UVA rays penetrate deeply, pass through glass, and are present year-round, even when the sky is overcast. Daily sun protection is the single preventive measure with the most well-documented effect in cosmetics.
Air pollution. Fine particulate matter settles on the surface and causes continuous oxidation.
Smoking. It increases collagenase production and reduces tissue oxygenation. It has a recognizable pattern, with pronounced periocular wrinkles and a grayish complexion.
Blue light. Much discussed and less decisive than is often claimed: the evidence mainly concerns pigmentation in darker phototypes. We discuss it in detail in the article on blue light and skin.
Sleep and stress. The peak of skin repair occurs during deep sleep, which chronic stress shortens first.
If I had to rank them by impact: daily sun protection, not smoking, getting enough sleep. They come before any serum, and no active ingredient can make up for their absence.
What a cosmetic product can and cannot do
It is worth being precise, because promises in this area are often disproportionate.
It can reduce oxidative stress with antioxidants, slow collagen degradation, support synthesis through peptides, improve hydration and surface firmness, even out skin tone, and prevent future damage with photoprotection.
It cannot recreate lost volume, reorganize already degraded elastic fibers, erase deep static wrinkles, or restore the structure of the dermis. When the goal is one of these, the appropriate field is aesthetic medicine, and it is right to know this before buying.
The dividing line, in practice, is this: lines that appear only when the face moves still have real cosmetic potential; those visible when the face is at rest have very little, because they correspond to a structural change in the dermis.
Where to start
In order of effectiveness, not price.
- Broad-spectrum sun protection, every morning, all year round. On its own, it is worth more than everything else put together.
- Antioxidants in the morning, to intercept free radicals before they trigger metalloproteinases. With a second benefit: they also slow the formation of cross-links that stiffen the fibers already present.
- Actives that support synthesis in the evening: peptides or retinoids, introduced one at a time and gradually.
- Keep the barrier in good shape. A compromised barrier remains inflamed, and inflammation accelerates everything else.
For the actives with the strongest evidence, see the dedicated article on the five actives against premature aging. The full range is in the LeLang selection of anti-aging treatments.
FERULIC + HA SERUM Vitamin C and ferulic acid face serum Antioxidant and tone-evening, with dual hyaluronic acid. Helps prevent dark sp... Discover FERULIC + HA SERUM
HYALURONIC ADVANCE Plumping face cream with hyaluronic acid, filler effect Multiple hyaluronic acid: hydrates from deep within to the s... Discover HYALURONIC ADVANCE
Understanding where you are — whether there is still room for prevention or whether you need to work on the underlying structure — is not always obvious in the mirror, and getting it wrong means waiting months to realize it. At LeLang partner pharmacies, you can find a pharmacist who can assess it.
Frequently asked questions
At what age does skin aging begin?
Earlier than you might think: fibroblasts already slow down between the ages of twenty-five and thirty, long before anything becomes visible. But the extrinsic component begins with the first sun exposure, so during childhood. That is why sun protection for children is an investment in the face they will have at fifty.
Do you need an anti-aging cream at thirty?
You need sun protection, as well as antioxidants. Actives that work on fibroblasts make more sense from the age of thirty-five onward. At thirty, a cream very rich in actives does no harm, but it does not add much either: the real leverage lies elsewhere.
Why do some people age better?
Genetics, skin type, accumulated exposure, and lifestyle, in varying proportions. The genetic component exists and is real, but it is the part we cannot influence; the factors we can influence still account for a very large share of the difference.
Does sunlight through glass count?
Yes, and that is exactly the truck driver’s story. Ordinary glass blocks UVB but lets much of the UVA through, which is primarily responsible for photoaging. People who drive a lot or work next to a window often have one side of their face that is more weathered than the other.
Can existing damage be recovered?
Partly. Skin tone, dark spots, hydration, and surface firmness improve noticeably. The deeper structure does not: it preserves what is already there. Anyone who promises to “reverse” aging is selling an expectation, not a result.
Is it better to prevent or treat?
Prevention, without question, because preventing damage costs much less than repairing it — in time, money, and achievable results. But the two are not mutually exclusive: at any age, prevention continues to pay off.
Sources for this article
01 Gordon J.R., Brieva J.C., Unilateral dermatoheliosis, New England Journal of Medicine, 2012; 366(16): e25.
02 Fisher G.J., Kang S., Varani J., Bata-Csorgo Z., Wan Y., Datta S., Voorhees J.J., Mechanisms of photoaging and chronological skin aging, Archives of Dermatology, 2002; 138(11): 1462-1470.
03 Krutmann J., Bouloc A., Sore G., Bernard B.A., Passeron T., The skin aging exposome, Journal of Dermatological Science, 2017; 85(3): 152-161.
04 Hughes M.C., Williams G.M., Baker P., Green A.C., Sunscreen and prevention of skin aging: a randomized trial, Annals of Internal Medicine, 2013; 158(11): 781-790.
05 Gkogkolou P., Böhm M., Advanced glycation end products: key players in skin aging?, Dermato-Endocrinology, 2012; 4(3): 259-270.
15-minute free consultation with the founder
Would you like to understand which mechanisms it makes sense to target for your skin, and in what order? Book a free virtual skincare consultation with Elisa Avalle, founder of LeLang.
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