Cold sore: Viruses or localised infections can cause the eye to redden â the problem usually starts in one eye, but can spread to both. The cold sore virus, which 90 per cent of us carry, can sometimes also infect the eye, causing inflammation.
Endorphins are chemicals, called peptides, that are made in the body. They have much of the same effect on a person as opium or morphine. As a result, they actually lower the feeling of pain in the body and can create a feeling of bliss or euphoria.
Until recently, much of what we've learned about endorphins has been gained from monitoring endorphins in the human bloodstream and in rats' brains. It wasn't possible to measure endorphin levels in the human brain without harming the subject, so the role of endorphins in the runner's high and other periods of euphoria or mood change were still hotly debated.