Chronically high levels of endogenous melatonin in children are healthy and normal. This hormonal state actively suppresses the maturation of the ovaries and testes, preventing puberty from starting until the appropriate age.
Light hitting specialized cells in the eyes activates a neural circuit to the midbrain. This triggers the release of the body's own opioids, such as beta-endorphins, which directly increases your tolerance for pain.
Melatonin isn't just for sleep; its release duration changes with seasonal light exposure. This acts as a hormonal calendar, signaling the time of year to your entire body and influencing major biological functions.
UVB light entering the eyes activates the sympathetic nervous system, which sends a direct signal to the spleen. This command prompts the spleen to deploy immune cells and molecules that actively search for and combat infections.
Specialized melanopsin cells in your eyes, not just skin, detect light to trigger stem cell turnover for hair, skin, and nails. This is the direct mechanism explaining why they grow faster during seasons with longer daylight hours.
UVB light exposure on the skin triggers a direct biological pathway that increases testosterone and estrogen. This hormonal shift enhances the desire to mate in both men and women, an effect independent of light exposure to the eyes.
Brief, daily exposure to 670nm red light rejuvenates aging retinal cells by improving mitochondrial function. In studies on individuals over 40, this non-invasive therapy restored age-related visual acuity decline by as much as 22%.
Many biological processes like hormone regulation and mood are triggered by light hitting non-visual melanopsin cells in the retina. Blind people who still have their eyes can activate these powerful health pathways through light exposure.
Viewing blue/UVB light between 10 PM and 4 AM activates a specific neural pathway from the eye to the perihabenular nucleus. This circuit actively reduces dopamine release, which can directly cause or worsen depressive symptoms, independent of sleep disruption.