Systemic effects like hormone increases, pain reduction, and immune status improvement are downstream consequences of illuminating large skin areas and providing adequate UVB exposure to the eyes.

“increases in hormones, reduction in pain by way of increases in enkephalin and other endogenous opioids, improving immune status by activating the spleen, and so on, and so on really are all the downstream consequence of illuminating large swaths of skin and making sure that those neurons within the eye get their adequate UVB exposure or other light wavelength exposure, not simply beaming a particular wavelength of light at a particular location on the body and hoping that that particular illumination at a particular location on the body is going to somehow change the biology at that location.”