Light spectrum in light therapy: white, blue or full spectrum?

When you start researching light therapy, you quickly come across a slightly confusing concept: the light spectrum.

White light, blue light, full spectrum… On paper, they all sound effective. But in practice, there are real differences — both in comfort and perceived effectiveness.

Here's what you need to know to make the right choice.

The light spectrum: what is it?

The light spectrum refers to the composition of the light emitted by the device.

Natural sunlight contains violet, indigo, blue, green, yellow, orange, and red.

This full combination is what influences our internal clock.

Light therapy devices therefore aim to reproduce this spectrum… with varying degrees of accuracy.

White light: the reference

The vast majority of lamps use a broad-spectrum white light.

Why?

  • It most closely resembles natural light.
  • It's comfortable for the eyes.
  • It allows for extended exposure.

It's the current recommended standard for:

  • seasonal fatigue;
  • low mood;
  • sleep disorders.

Personally, this is the type of light I use every day.

Blue light: more targeted, but more intense

Some lamps — and especially light therapy glasses — use a blue-enriched light.

Why blue?

Because this spectrum acts directly on the photosensitive cells in the retina that are responsible for:

  • regulating melatonin;
  • wakefulness;
  • alertness.

Advantages:

  • effective at lower intensities;
  • more compact devices;
  • more flexible exposure.

Disadvantages:

  • more visually stimulating;
  • less comfortable for static sessions.

That's why you'll mostly find this spectrum in glasses.

Full spectrum: marketing or genuine benefit?

The term "full spectrum" is widely used… but sometimes overblown.

In theory, it refers to a light that reproduces the full visible solar spectrum.

In practice:

  • all good white lamps are already broad-spectrum;
  • the real difference is often minimal;
  • effectiveness depends mostly on lux output.

In other words: a certified 10,000-lux white lamp beats a marketing "full spectrum" lamp with low output every time.

Spectrum and visual comfort

Spectrum has a big impact on comfort:

Spectrum Comfort Best use
White light Very comfortable Morning sessions
Blue-enriched More stimulating Glasses / on the go
Full spectrum Variable Versatile use

UV: an essential point

Whatever the technology, a light therapy lamp must be:

  • UV-free
  • Medically certified

UV rays bring no benefit for light therapy and can be harmful to:

  • the eyes
  • the skin

Fortunately, all serious lamps are UV-free.

My experience after testing both

Having used a white lamp and blue-spectrum glasses:

  • White light is more pleasant in the morning
  • It fits better into a coffee-and-reading routine
  • Blue is more practical when on the move

I didn't notice a major difference in effectiveness… but a real difference in comfort.

Which spectrum should you choose?

  • For a lamp: white light, 10,000 lux
  • For glasses: blue-enriched spectrum
  • For daily comfort: broad-spectrum white

The most important factors remain:

  • Intensity (lux)
  • Consistency
  • Session duration

Key takeaways

  • Spectrum affects comfort more than effectiveness.
  • White light is the reference standard.
  • Blue is more targeted but more stimulating.
  • Full spectrum is often just a marketing term.
  • UV-free is non-negotiable.

Further reading