Figure 7.

Stressed skin regulates the central HPA axis. Signals generated in stressed skin are delivered either by ascending nerve routes to the brain or by circulation to the hypothalamus, pituitary, or adrenal gland, which would depend on the nature and intensity of the stressor and on skin anatomy/histology. Furthermore, UVR production and secretion of final effectors of the HPA (glucocorticoids) is activated by sequential and/or alternative modes of action originating in the skin that will depend on the wavelength and dose of solar electromagnetic energy.