More than just sunburn: how different types of light affect your skin – from UVB to infrared

A sunburn is the only thing you really feel from the sun – and that’s exactly what misleads you. The part of sunlight that causes sunburn accounts for only a narrow band at the edge of the spectrum. The far greater proportion, which causes your skin to age over the years, reaches you without you even noticing.

Of the sunlight that reaches the ground, only around five per cent is UV radiation. Visible light and infrared account for the vast majority of the rest. And when you measure where in the skin the free radicals that break down collagen are formed, the usual picture is turned on its head: in a Analysis Around half was attributable to visible light, 46 per cent to UVA – and only 4 per cent to UVB, which is precisely the part that causes sunburn. Let’s go through the spectrum, from sunburn to invisible heat.

UVB: the part that causes sunburn – and produces vitamin D

UVB is short-wave radiation. It does not penetrate deeply, but is sufficient to cause sunburn and direct damage to the genetic material of skin cells – which is why UVB is linked to skin cancer.

At the same time, UVB is the only type of light that enables your skin to produce vitamin D: it converts a precursor in the skin into vitamin D3. That might sound like an argument in favour of sunbathing, but it isn’t. Even brief periods with your face and arms uncovered, a few times a week, are enough. Beyond that, your skin doesn’t produce any more vitamin D; it simply accumulates damage. It doesn’t work through window glass anyway – UVB doesn’t get through (UVA does, but more on that in a moment). And in Zurich, from around November to March, the sun is too low in the sky to produce any vitamin D at all; during this period, you’ll need to get it from your diet or a supplement. One more piece of reassurance for anyone who wears sun cream every day: Studies show that regular users do not have a vitamin D deficiency. You don’t have to choose between protection and vitamin D.

UVA: deep, invisible, all year round

UVA penetrates much deeper, right down to the dermis. It rarely causes sunburn, but over the years it breaks down collagen and elastin and promotes the formation of pigmentation spots. This makes UVA radiation the driving force behind premature skin ageing. And it is persistent: UVA is present all year round, even when the sky is overcast, and it passes through window glass – in the car, or at your desk by the window.

For our pre-ageing skincare, UVA is therefore the real enemy. And this is precisely where good sun protection makes all the difference: not the SPF number, which only protects against sunburn, but strong UVA protection, indicated by the UVA symbol in a circle or the PA++++ rating. We’ve summarised what really matters here broken down in a separate post.

The sun’s still shining even when you’ve long since gone indoors

And here is the finding that turns everything on its head. For a long time, it was assumed that UV damage occurs the moment the light hits the skin. Research from Yale has shown that this is only half the story.

In the skin’s pigment cells, the typical UV-induced damage to genetic material continues to develop for over three hours, once the UVA exposure is long over. Half of this damage occurs in the dark. There is a roundabout process behind this: UV light breaks down the pigment melanin into tiny fragments, whose energy is slowly released and only reaches the DNA hours later – as if a UV photon were arriving late.

The researchers put it this way: we underestimate UV damage because we always take measurements immediately after sun exposure. For you, this means one thing above all: the sun’s effects don’t stop just because you go indoors.

Blue light: it’s the sun that’s the problem, not your screen

Visible light is not as harmless as it sounds – particularly the blue, high-energy portion, known as HEV for short. It actually penetrates deeper than UVA and UVB, reaching as far as the dermis.

Blue light from the sun can trigger persistent pigmentation, particularly in darker skin types and in cases of melasma; the pigment cells have their own sensor for this. It also generates free radicals, which activate collagen-degrading enzymes and deplete the skin’s own antioxidants – recovery from this can take up to a day. This is why tinted sun creams containing iron oxide are beneficial for skin prone to pigmentation.

And what about screens? A lot of fear is being peddled here, which the figures do not support. The blue light emitted by mobile phones and laptops is, within the same wavelength range, a hundred to a thousand times weaker than that of the sun. The total amount of exposure accumulated over the course of a day spent in front of a screen remains well below the threshold at which pigmentation changes at all. In a controlled trial A group sat in front of a bright screen for eight hours a day over five days – the melasma did not get any worse. So the idea of «digital ageing» caused by your screen is exaggerated. If you want to protect yourself from blue light, protect yourself from the sun. Long-term data on screens is still limited, but based on what we know today, your laptop isn’t the problem.

Infrared: near, far – and surprisingly controversial

That leaves the largest and warmest part of the spectrum: infrared. It ranges from 760 nanometres to well beyond and is divided into three bands. Near-infrared (IR-A) penetrates the deepest – over 65 per cent of it reaches the dermis. The mid- and far-infrared (IR-B and IR-C) remain closer to the surface. Infrared accounts for more than half of the sun’s energy, with a good third of that being IR-A.

A research group based in Düsseldorf has investigated in particular the effects this has on the skin. In the dermis, near-infrared light triggers the production of free radicals via the mitochondria and increases levels of MMP-1, the most important collagen-degrading enzyme – in living skin in around 80 per cent of the test subjects, and at the same time it reduces the skin’s antioxidant levels. Added to this is the heat itself: in the sun, the skin heats up to over 40 degrees, and this, too, accelerates collagen breakdown.

That’s one side of the story. The other is just as important, because it is rarely discussed: the extent to which infrared light causes ageing in real life is a matter of debate. Many of these studies used artificial infrared lamps that do not replicate the solar spectrum, and disregarded the heat. A Review article calculated that the annual infrared dose from normal sun exposure is roughly equivalent to that received by blast furnace workers – who show hardly any chronic skin damage – and therefore considered it premature to incorporate infrared protection into sun creams and use it to market products as a means of combating skin ageing. According to other studies, at realistic doses, near-infrared radiation might even have a neutral effect.

Our take on this: Infrared penetrates deeply and is biologically plausible – but the claim «blocks infrared» on packaging is not backed by evidence. Don’t buy a product based on this claim.

Why we at Dermalux use infrared ourselves

Which brings us to an obvious question. If near-infrared light can cause the skin to age – why do we at Dermalux shine it on you?

The answer is the most interesting part of this article, and it leads back to the mitochondria, the powerhouses of every cell. Red light (around 633 nanometres) and near-infrared light (around 830 nanometres) are absorbed there by an enzyme called cytochrome c oxidase. When the cell is under stress, a molecule – nitric oxide – blocks this enzyme and slows down energy production. The light release this brake: The enzyme starts working again, and the cell produces more ATP, its energy currency. More energy means greater capacity to repair and build collagen.

The catch lies in the dose. The same wavelengths have a stimulating effect in small, controlled quantities – but in large, uncontrolled quantities, they can have the opposite effect. And unlike UV light, red and near-infrared light do not have any genotoxic effects.

Our Dermalux It works with three wavelengths: blue (415 nm) to combat the bacteria that cause acne, red (633 nm) to stimulate collagen production and soothe the skin, and near-infrared (830 nm) for deeper repair. The 830-nm light lies within the same near-infrared range as the sun’s IR-A – yet it works in the opposite way. The difference lies in five key points: no UV; individual, specifically selected wavelengths rather than a broad spectrum; controlled application over a few minutes rather than years of uncontrolled exposure; no uncontrolled heat; and the direction of action, namely building up collagen rather than breaking it down.

This also resolves the apparent contradiction from the chapter on infrared. To say that «infrared causes ageing» is an oversimplification. What matters are the dose, the wavelength and the context in which the light strikes the skin.

What really protects you

If there’s one thing you take away from this article, let it be this: UVA, visible light and infrared all lead to the same mechanism – oxidative stress, i.e. free radicals. That’s exactly where protection needs to start, rather than trying to tackle every type of radiation with a separate gadget.

What really makes a difference is straightforward. A sunscreen with strong UVA protection covers the area that has been proven to contribute most to skin ageing; what you look out for and which we recommend, is covered elsewhere. Anyone prone to pigmentation spots or with a darker skin tone is better off using a tinted version containing iron oxide, as this also blocks visible light. When it comes to the sun’s heat, shade, a hat and avoiding the midday heat are more effective than any «anti-infrared» product.

And then there are the antioxidants. They target precisely the common denominator: the free radicals generated by UVA, infrared and visible light. Vitamin C neutralises free radicals and is also a building block for collagen formation; the copper peptide GHK-Cu supports collagen and the skin’s own defences. In the studio, a HydraFacial Antioxidants are delivered directly into the skin, and Dermalux uses restorative red and near-infrared light.

Exactly how antioxidants work – whether they come from a jar or from a plate – is a topic in its own right; we’ll be looking at that in our next article.

Not sure what your skin really needs?

With a free AURA 3D skin analysis, we examine your skin right down to its deeper layers and identify where it needs protection and support. Book your free AURA 3D skin analysis in Zurich now.