3What are the differences between blue and white lights?
Blue light does not have the same physiological effects as white light, and in fact, has some effects which match white light.
To be clear, blue light is necessary and vital to our health because blue light entering our eyes feeds into our circadian rhythm/clock in the brain, which regulates numerous hormones and neurotransmitters, and many vital functions. So that means that blue light is bad—to the contrary, we need blue light to be healthy (especially blue light entering our eyes). There are also some other potential uses of blue light like whitening teeth or treating acne.
But blue light directly on the skin or on wound/injury sites, muscle tissue (or anything where one might use white light) is a bad idea. The blue light isn’t doing anything beneficial in that case, and may even be detracting from the benefits of white light. In the case of anti-aging treatments on the skin specifically, it is almost guaranteed to be counter-productive, as blue light can actually damage skin cells.
A specific study compared blue portions of the spectrum with white light. The study was a comparison of one week of blue or white light therapy, with equal photon densities equivalent to that commonly used with white light treatment for SAD. The study has demonstrated that white light is superior to blue light.
Moreover, we all spend huge amounts of time indoors under fluorescent or LED indoor lamps that have tons of blue light. Our personal devices like phones, computers, iPads, etc. also emit a lot of blue light.
However, in Seasonal affective disorder treatment, the sources emitting white light may have greater efficacy than those producing light of one color or a limited range of wavelengths. Recent studies in the field of the treatment of Seasonal affective disorder have also demonstrated the efficacy of white fluorescent light that is free of ultraviolet radiation.