Sunlight is not a single thing. It is a spectrum that changes in composition throughout the day, and that change has direct effects on your skin. What the sun emits early in the morning differs significantly from what you get on your skin at two in the afternoon. This is not a detail. It is at the core of how your body processes sunlight — and it explains why infrared light, long considered a secondary matter, is increasingly seen as a key element in skin protection.
In this article, we explain how the solar spectrum shifts throughout the day, what infrared light does to your skin, and what science says about the protective effect of near-infrared during UV exposure.
The sunlight spectrum is not the same all day
Sunlight consists of three main components: ultraviolet light (UV), visible light, and infrared radiation. The ratio between these three constantly shifts as the sun takes a higher or lower position in the sky.
In the early morning, when the sun is still low, the light that reaches the earth is richer in red light and near-infrared. UV radiation is then minimal, because the sunlight travels a longer path through the atmosphere and a large part of the UV wavelengths is filtered out. The sun is literally too low for strong UV exposure.
As the day progresses and the sun approaches its highest point, the balance shifts. <cite index="28-1">UVB rays fluctuate throughout the day and are strongest around noon.</cite> At that moment, the UV intensity is at its peak and the infrared fraction is relatively lower. The situation then slowly reverses: in the late afternoon and evening, the red and infrared wavelengths dominate again, while UV gradually decreases.
This pattern is not evolutionarily accidental. Our skin has developed over millions of years in an environment where this daily rhythm of light was always present.
What is IR-A and how does it relate to UV?
Infrared radiation is divided into three zones: IR-A (760-1400 nm), IR-B (1400-3000 nm), and IR-C (above 3000 nm). The part that is relevant for skin protection and daily sun exposure is IR-A, also called near-infrared or NIR.
Of the total solar radiation that reaches the Earth's surface, infrared A, B, and C together make up about 40 percent. About 40 percent of that is IR-A. This means that natural sunlight produces IR-A radiation of approximately 20 mW/cm². For comparison, UV radiation constitutes only 6.8 percent of the solar spectrum that reaches the ground. Visible light accounts for nearly 39 percent.
Most attention to skin damage goes to UV — and rightly so, because UV can directly cause DNA damage. But the question that has increasingly occupied researchers in recent years is what the other 93 percent of the spectrum actually does. And more specifically: is IR-A a friend or an enemy of the skin?
The study that put everything into perspective
In 2016, dermatologist Daniel Barolet from McGill University, François Christiaens, and Michael R. Hamblin from Harvard Medical School published a review in the Journal of Photochemistry and Photobiology B: Biology, titled 'Infrared and Skin: Friend or Foe.' It became one of the most cited review articles on this topic.
Their central argument was that previous studies showing damage from infrared on the skin used artificial light sources with an intensity far above actual sunlight. <cite index="16-1">In studies where cells were exposed to a minimal IR-A radiation of 333 mW/cm² or in other studies to 105 mW/cm², both intensities were far above what the sun actually produces. In reality, the IR-A radiation from the sun is about 20 mW/cm².</cite>
In other words: the lab conditions that showed damage were not representative of how we experience infrared in daily life.
But Barolet and his colleagues went beyond merely criticizing previous research. <cite index="18-1">They suggested that IR-A may precondition the skin, a process referred to as photoprevention. From an evolutionary perspective, exposure to IR-A wavelengths in morning sunlight prepares the skin for the harmful UV radiation that follows later in the day. IR-A is therefore more the solution than the problem. It does more good than harm for the skin. Ultimately, it comes down to intensity.</cite>
Photo prevention: the skin that prepares itself
The mechanism that Barolet describes is called photoprotection or preconditioning. The idea is that morning IR-A exposure activates biological protective pathways in the skin, making it more resistant to the UV peak around noon.
<cite index="20-1">Multiple in vitro studies have shown that preconditioning fibroblasts with NIR can protect them against upcoming UVB damage via p53 cell signaling pathways that induce anti-apoptotic effects. In the first in vivo study, subjects were treated with 660 nm light prior to UVB exposure. The results showed a reduction of the UVB-induced erythema response in a significant number of the pretreated subjects. An SPF-15-like sun protection effect was also observed, as well as a reduction in post-inflammatory hyperpigmentation.</cite>
An SPF-15-equivalent effect through preconditioning with near-infrared light. That is not a marginal finding. SPF 15 blocks about 93 percent of incoming UVB rays. The comparison indicates how substantial the biological protection mechanism can be when the skin is well prepared.
Moreover, follow-up experiments showed that wavelengths in the near-infrared spectrum provided the strongest protection, with superior reduction of erythema compared to 660 nm alone.
What infrared does to collagen and moisture
In addition to protection, near-infrared also has direct restorative effects on the skin structure itself. This distinguishes it from ultraviolet, which even at low doses breaks down collagen through the activation of matrix metalloproteinases (MMP-1).
<cite index="34-1">Photobiomodulation stimulates collagen production through a mechanism in which red and near-infrared light affect cytochrome c oxidase in the mitochondria, increase ATP production, and activate signaling pathways that promote fibroblast proliferation. This leads to increased production of collagen and elastin, and to a reduction in enzyme activity that breaks down collagen.</cite>
Concretely: where UV destroys collagen, near-infrared stimulates its production. And where UV dries out the skin through oxidative damage to the lipid barrier, infrared works exactly the opposite. <cite index="37-1">Regular infrared exposure improves the skin's ability to retain moisture. As circulation improves and the skin barrier strengthens, transepidermal water loss decreases. The result is a more supple, hydrated skin that is less prone to dull spots and peeling.</cite>
This difference in effect on the skin's moisture balance is one of the most practically relevant distinctions between UV and IR-A.
How this translates to a daily routine for the skin
The science behind photoprevention and the day-night pattern of the solar spectrum has a direct practical implication: the timing of light exposure is relevant.
Early morning light is rich in near-infrared and relatively poor in UV. <cite index="26-1">As the sun sets, the spectrum shifts towards red and infrared. In the early morning and around noon, sunlight is richer in blue light and UV. As the sun sets, the spectrum shifts towards red and infrared.</cite>
That is exactly the situation that the skin has synchronized over millions of years: first infrared as warming and preparation, then UV at the peak of the day. The sequence is biologically meaningful.
For people who are rarely outside in the early morning, or who consciously avoid UV exposure but still want to take advantage of the benefits of the light spectrum, targeted infrared or red light therapy at home offers a way to consciously apply that preparation regardless of season, cloudiness, or work schedule.
What the skin cannot tolerate: the difference between therapeutic and harmful
One of the points of confusion in the discussion about infrared and skin is that laboratory studies with extremely high intensities sometimes showed damage. It is important to put this into perspective.
Medical devices and cosmetic tools use infrared technology in a precise manner, with selected wavelengths of approximately 600-900 nm, low intensities of approximately 10-50 mW/cm², and limited exposure times of 15-30 minutes per session. This is intended to harness the benefits and minimize the risk of side effects.
The harmful effects found in some studies occurred at intensities of 105 to more than 300 mW/cm², which corresponds to multiple hours of tropical midday sunlight in a single session. That is not a representative situation for daily use of a therapeutic lamp.
Comparison: what does UV do, and what does IR-A do?
| UVB | GRAPE | Near-infrared (IR-A) | |
|---|---|---|---|
| Penetration depth | Epidermis | Deep dermis | Deep dermis and subdermal tissues |
| Collagen | Breaks down via MMP-1 | Breaks down via free radicals | Stimulates production through fibroblast activity |
| Fluid balance | Dries out skin | Damages lipid layer | Improves moisture retention, reduces TEWL |
| Hyperpigmentation | Stimulates melanin production | Deeper pigment effect | Can reduce post-inflammatory hyperpigmentation |
| Combustion | Yes, primary cause | No, but DNA damage | No, no ionizing effect |
| Restorative effect | None | None | Yes, via photobiomodulation |
| Preconditioning | Possible via UVB, but ionizing risk | Not described | Yes, demonstrated in vivo |
Frequently Asked Questions
Can infrared prevent sunburn?Infrared does not replace sunscreen. Photoprevention is a biological mechanism that reduces the skin's response to UV, similar to an SPF-15 protection level with preconditioning using 660 nm light just before UV exposure. Sun protection at high UV intensity still requires adequate protection.
Can I combine infrared therapy with sun exposure?Yes. Therapeutic use in the morning aligns with the natural pattern of the sun spectrum. Always use home equipment at the recommended intensities and times.
Does infrared dry out the skin?No. This is one of the distinguishing characteristics compared to UV. Near-infrared improves the skin's moisture barrier and reduces transepidermal water loss.
Is infrared the same as heat from the sun?Not exactly. All sunlight feels like infrared, but therapeutic infrared uses specific wavelengths (630-900 nm for near-infrared) at low intensities. The mechanism of action is primarily biological, not thermal.
When is the best time to use infrared?Early in the morning aligns with the natural pattern of the light spectrum. This is also the time when the circadian rhythm is most receptive to red and infrared light.
Sources
- Barolet, D., Christiaens, F., & Hamblin, M.R. (2016). Infrared and skin: Friend or foe.Journal of Photochemistry and Photobiology B: Biology, 155, 78–85.PubMed
- Schieke, S.M., Schroeder, P., & Krutmann, J. (2003). Cutaneous effects of infrared radiation: from clinical observations to molecular response mechanisms.Photodermatology, Photoimmunology & Photomedicine, 19(5), 228–234.
- Wunsch, A., Matuschka, K. (2014). A controlled trial to determine the efficacy of red and near-infrared light treatment in patient satisfaction, reduction of fine lines, wrinkles, skin roughness, and intradermal collagen density increase.Photomedicine and Laser Surgery, 32(2), 93–100.PMC3926176
- Effects of Infrared Radiation on Skin Photo-Aging and Pigmentation.PMC2687728
- Eucerin (2025). Sunlight: influence of UVA and UVB on your skin.eucerin.nl
- Dr. Jetske Ultee (2026). Why you sometimes still get damage even when using sunscreen.dr-jetskeultee.nl
Disclaimer: This article is informative in nature and does not replace medical advice. In case of skin complaints or doubts, always consult a dermatologist or skin therapist.
