Does pollution really age the skin?

For decades, the answer to the question "what ages the skin?" had two names: sun and tobacco. In the last 15 years a third has been added, especially for people living in cities: air pollution. "Anti-pollution" cosmetics, "urban shield" serums and promises of protection against invisible particles have appeared.

Behind the marketing there is real science, but more modest and more specific than the packaging suggests. This article explains what the studies show, how pollution may act on the skin and what actually helps.

Which pollutants and how they reach the skin

"Pollution" is a mixture of different substances, with different behaviours on the skin.

The skin is a good barrier, but it is not impermeable. Pollutants can reach the cells by three routes:

• Directly, through the stratum corneum, especially when the barrier is weakened.
• Via the hair follicles, where the smallest particles can accumulate.
• Via the bloodstream, after being inhaled.

The effect is mainly cumulative: it is not one day of heavy traffic that marks the skin, but years of exposure.

What the studies say

The German study that opened the subject

In 2010, German researchers published the results of a study of around 400 women aged between 70 and 80, living in urban and rural areas of the Ruhr region (the SALIA study). They assessed long-term exposure to traffic-related particles and compared it with signs of skin ageing, measured on a standardised scale (Vierkötter et al., 2010).

Main results:

• Greater exposure to traffic particles was associated with more pigmented spots on the forehead and cheeks (the authors reported around 20% more spots for an increase in exposure to soot and particles).
• It was also associated with more marked nasolabial folds.
• The associations held after accounting for age, sun exposure, tobacco and phototype.

Confirmation in different populations

In 2016, a second study analysed two very different populations (Hüls et al., 2016):

• 806 German women (mean age 73).
• 743 Chinese women from the Taizhou region (mean age 59).

The focus was nitrogen dioxide (NO₂), a typical traffic pollutant. In both populations, exposure to NO₂ was associated with more dark spots (lentigines) on the cheeks: around 25% more for every 10 µg/m³ increase. Interestingly, there was no association on the backs of the hands and the forearms, which the authors interpret as a sign that the face, more exposed to the air, is more affected.

How to read these results

• These are association studies. They show that people who live with more pollution tend to have more dark spots, but they do not on their own prove that pollution causes them. Factors such as income, occupation or habits may act as confounders.
• They mostly involve older women, with decades of exposure.
• They are consistent across populations and have a plausible biological explanation, which strengthens the likelihood that the effect is real.
• The effect seems more evident on dark spots than on wrinkles.

How pollution may act on the skin

The most studied mechanisms are:

• Oxidative stress. Particles, PAHs and ozone generate free radicals that deplete the skin's natural antioxidants. In experimental studies, ozone reduced vitamin E in the stratum corneum and oxidised surface lipids (Thiele et al., 1997).
• Activation of the AhR receptor. PAHs bind to a receptor in skin cells which, when activated, stimulates the production of melanin and of enzymes that break down collagen. It is one of the most accepted explanations for the association with dark spots.
• Inflammation. Pollutants induce inflammatory mediators that, in a chronic, low-grade way, contribute to ageing (sometimes called "inflammaging").
• Alteration of the skin barrier. Oxidation of surface lipids weakens the barrier, which makes it easier for more pollutants to penetrate and for water to be lost.

The synergy with the sun

One of the most important aspects is that pollution and solar radiation seem to add up and boost each other:

• Some PAHs absorb UVA radiation and become even more reactive when exposed to light (phototoxicity).
• Ozone forms precisely in intense sun.
• Both deplete the same antioxidants in the skin.

In practice, this means that the most effective measure against the effects of pollution on the skin is probably the same as against photoageing: protecting from the sun.

Indoor pollution and tobacco smoke

Pollution is not only outdoors.

• Cooking with solid fuels. In a study of Chinese women, regularly cooking with wood or coal in poorly ventilated spaces was associated with more marked facial wrinkles and more fine wrinkles on the backs of the hands (Li et al., 2015). It is a rare situation in Portugal, but it is a reminder that indoor exposure counts.
• Fireplaces, wood-burning stoves and grills produce particles and PAHs; good ventilation reduces exposure.
• Tobacco smoke. It is the most concentrated source of pollution that many people expose themselves to. Smoking is associated with early facial ageing in twin studies and large cohorts (Guyuron et al., 2009). Passive smoke also exposes the skin to these pollutants.

Pollution and other skin diseases

Besides ageing, pollution has been linked to worsening of:

• Atopic dermatitis (eczema), especially in children.
• Acne, in some studies.
• Sensitive, reactive skin, with more redness and discomfort.
• Dark spots and melasma, in line with the pigmentation studies.

The evidence varies from condition to condition and is generally weaker than for dark spots.

What you can do

It is not possible to stop breathing city air. But it is possible to reduce the impact on the skin with simple measures, almost all useful for other reasons too.

1. Sunscreen every day

Given the synergy between pollution and radiation, this is the most important measure. A broad-spectrum sunscreen, applied in the morning to the face, neck and hands, reduces the combined damage from sun and pollutants. For people prone to dark spots, a tinted sunscreen adds protection against visible light: see Tinted sunscreen: how to choose and how to apply.

2. Gentle cleansing at the end of the day

Removing sunscreen, make-up and particles that have built up on the surface of the skin at the end of the day makes sense, especially for people who spend the day in an urban environment. Use a gentle cleanser, without alkaline soap; cleansing too hard or too often weakens the barrier, which is precisely the defence against pollutants.

3. Topical antioxidants in the morning

Vitamin C, vitamin E, ferulic acid, niacinamide and other antioxidants reinforce the skin's defences against oxidative stress. The direct evidence against pollution is mainly laboratory-based, but the logic is coherent and the same actives have demonstrated benefits against sun damage. We explain this in Antioxidants for the skin: vitamin C, E and ferulic acid explained without exaggeration.

4. Healthy skin barrier

An intact barrier lets fewer pollutants through. Moisturisers with ceramides, cholesterol and fatty acids, and avoiding irritating the skin with too many actives, are part of the protection.

5. Reduce exposure whenever possible

• Prefer routes on foot or by bicycle away from the busiest roads.
• Check the air quality index (in Portugal, provided by the Portuguese Environment Agency) on days with pollution episodes.
• Ventilate the home well when cooking and avoid fireplace smoke indoors.
• Do not smoke and avoid passive smoke.

What about "anti-pollution" cosmetics?

To date, there is no standardised, consensus test method to demonstrate that a cosmetic protects the skin from pollution. Many products base their claim on laboratory tests (particles that adhere less to a surface, for example) that say little about the effect on the skin over years. In general, an "anti-pollution" product is useful to the extent that it has good antioxidants, protects the barrier or contains UV filters, and not because of the claim itself.

At Luxmed, we help you put together a simple routine for people who live and work in the city: sun protection, appropriate cleansing, antioxidants and barrier care, without piling on products. In the clinic, facial treatments help even out tone and treat dark spots that are already established.

This article is for information purposes and does not replace a medical consultation. The results of any product or treatment vary from person to person.

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