What is phototherapy?

What is phototherapy?

Phototherapy is a new non-invasive therapeutic alternative that has revolutionized the management of different conditions and pathologies.

It consists of the conversion of light energy, within the visible light spectrum, into chemical and physical reactions that induce therapeutic changes in the patient.

It works with the visible light spectrum, achieving different types of effects at the molecular and cellular level, including the destruction of some specific bacteria.

The visible spectrum

Humans are able to see color at wavelengths ranging from 400 nanometers (violet) to 700 nanometers (red).

It is for this reason that this range is called the visible spectrum. The human eye is not capable of seeing color outside that range, but other organisms can.


When we talk about phototherapy, we talk about frequencies measured in wavelength.

It is electromagnetic radiation at such a high frequency that it is measured by the distance between peaks.

  • Long length > lowest frequency
  • Short length > higher frequency

Thus, each wavelength corresponds to a specific color within visible light.

The wavelengths of visible light are:

  • Violet: 380 to 450 nm
  • Blue: from 450 to 495 nm
  • Green: from 495 to 570 nm
  • Yellow: from 570 to 590 nm
  • Orange: from 590 to 630 nm
  • Red: from 620 to 750 nm

How phototherapy works

Depending on its wavelength, it will act on some molecules or others in a totally selective way, thus being able to perform the desired treatment, such as acne, alopecia or photoaging.

Those molecules capable of interacting with light by absorbing its energy are the chromophores and each wavelength has a specific chromophore.

Are RGB emitters suitable?

There are RGB light emitters on the market that are sometimes advertised as phototherapy. However, these emitters, not having that wavelength, have no effect on bacteria.

RGB emitters emit in these three wavelengths, red, green and blue, acting in a totally non-specific manner. The rest of the colors are mixed, just like a television.

For example, for an acne treatment, phototherapy at 420 nm reacts with porphyrins killing P. acnes bacteria.