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.
Endorphins perform several functions, but their best-known one is acting as a painkiller and a reward, causing a feeling of euphoria. Endorphins lock onto cells called opioid receptors, blocking the transmission of pain signals. Everyone has different triggers for endorphins, but common stimuli are pain, food and sex.