What is blue light?

Light is a form of electromagnetic radiation emitted by a light source (e.g., the sun, light bulbs, displays, etc.) in the form of waves. The human eye can only perceive a small portion of the entire electromagnetic spectrum. Light wavelengths are measured in nanometers (nm). The visible spectrum for us ranges from 380 to 780 nm and includes all the colors of the rainbow. Wavelength determines how energetic the light is. The shorter the wavelength, the more energetic the light.

Blue light is high-energy, short-wavelength light in the range of 400–495 nm and is part of the visible light spectrum of daylight and artificial light.

The visible light spectrum

Blue light is short-wavelength light between 400 and 495 nm and is therefore significantly more energetic than, for example, red light between 630 and 780 nm. This high energy directly affects our bodies: through light-sensitive cells in the retina, blue light acts on the so-called suprachiasmatic nucleus (SCN), the control center of our internal clock. There it regulates, among other things, the release of the sleep hormone melatonin and can thus significantly influence our sleep-wake cycle.

Melatonin is an endogenous hormone produced by the pineal gland in the brain that regulates the sleep-wake cycle.

Natural blue light ☀️

In nature, blue light never appears in isolation, but always in balance with other wavelengths, embedded within the spectrum of sunlight. Natural sunlight includes all colors and is therefore referred to as full-spectrum light.

Difference between sunlight spectrum, full-spectrum LED and standard LED

Over the course of the day, this color spectrum changes continuously: in the morning and evening the share of red and infrared light is higher, while at midday there is more energetic, blue light.

Color of sunlight depending on time of day

This balance and the change in the light spectrum throughout the day are essential for our internal clock. During the day, natural blue light is activating, lifts mood and promotes alertness and concentration. It suppresses melatonin production while simultaneously boosting the production of dopamine and serotonin. Both are neurotransmitters that support drive, motivation and a good mood. In addition, it positively influences our metabolism, hormone regulation and the immune system.

In sunlight, blue light is embedded in a balanced color spectrum — this natural balance supports our internal clock and promotes mood, concentration and many bodily functions.

Artificial blue light 📱

Blue-light spectrum of LED, tablet and smartphone

It’s different with artificial light sources. In the modern world, we are increasingly exposed to artificial blue light in the evening and at night, especially from LED lamps, smartphones, TVs and computer screens. Like natural light, artificial light also contains a mix of different wavelengths — but without the crucial balance across all colors. Artificial light often has a high blue component because it allows for high luminous efficacy in an energy-efficient way. That’s an advantage for power consumption, but not for our body and well-being.

Whether we watch our favorite series in the evening, scroll through social media on our smartphones or turn on the lights at home, each time we send our brain the signal that it’s still the middle of the day and the sun is shining. This unnatural exposure to artificial blue light — even when it’s only a weak blue light — suppresses melatonin production at night and robs us of valuable sleep.

When the body is exposed to artificial blue light in the evening, it can negatively affect our circadian rhythm, sleep and, in the long term, our health.

Conclusion: Blue light — friend and foe

Blue light is not inherently bad — quite the opposite. During the day, it’s essential for a healthy sleep-wake rhythm, good mood and mental performance. It becomes problematic, however, when we are continuously exposed to artificial light in the evening or indoors during the day without getting enough natural light. That throws our natural rhythm out of balance.

Blue light matters — but at the right time. What counts is the dose and when you’re exposed: activating during the day, better avoided in the evening.

What you can do ✅

You can effectively support your natural circadian rhythm with simple habits:

Start your day with natural light

Getting natural morning light is one of the most important steps for your sleep and energy levels. Ideally, go outside for a few minutes right after waking up. A short walk is enough to activate your internal clock and lift your mood.

But even if you don’t have time or the possibility to go outside in the morning, there are alternatives: have breakfast next to an open window on the sunny side, enjoy a coffee on the balcony, or simply soak up some light in the brightest room in your home — all of this already helps! The key is to let unfiltered daylight directly into your eyes (without sunglasses or window glass in between).

Woman having breakfast in the sun on her balcony

Get as much daylight as possible

Try to integrate natural light into your day as often as possible. Work near a window or take calls by the window or outdoors.

A short walk during your lunch break can work wonders for your mind, your sleep and your overall well-being. Often just 10–15 minutes are enough to give your body the light signal it needs. Small steps count!

Avoid artificial blue light in the evening

In the evening, reduce artificial light sources with a high blue component. Standard LED lamps, displays and screens emit blue light that signals to your body it’s still daytime. Use blue-light-free light sources where possible, such as warm, red light or specially designed lamps. Dimming rooms with softer lighting also helps to support evening melatonin production.

Woman looking at her smartphone in the evening, experiencing the effects of blue light on eyes and sleep

Wear blue-blocker glasses in the evening

If you’re still working at a screen or watching shows in the evening, wearing a blue-light-filter (blue-blocker) pair of glasses can help a lot. These glasses specifically block high-energy blue light, allowing your body to wind down and release melatonin. That’s especially important for restorative sleep.

Woman on the sofa in the evening wearing her Sleep blue-blocker glasses by Lichtblock

Use blue-blockers during the day only with lots of artificial light

During the day we need natural light — especially the blue component — to keep our body alert and performing well. Therefore: if you work at a screen in a bright office with plenty of daylight, wearing a blue-light-filter pair of glasses is usually not necessary. In fact, it can even be counterproductive because you’re withholding important light signals from your body.

It’s different if you spend much of your day in spaces with purely artificial lighting, e.g., supermarkets, department stores, warehouses/production halls or windowless offices with LED lighting. Here, the natural balance in the spectrum is missing and artificial light from screens and lamps often contains an excessively high blue share. In such environments, a daytime blue-blocker with a light filter can help balance the spectrum, relieve your eyes and reduce issues such as headaches, burning eyes or concentration problems.

Woman working in a home office wearing blue-blocker glasses