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.
The release of endorphins has an addictive effect, and more exercise is needed to achieve the same level of euphoria over time. In fact, endorphins attach to the same neuron receptors as opiates such as morphine and heroin (12) .