Temporary loss of consciousness caused by reduced blood flow to the brain. The medical term for this is ‘syncope’.
Episodes of fainting are commonly due to a vasovagal attack – an episode in which overstimulation of the vagas nerve (which controls the vital organs such as the heart and lungs) causes slowing of the heartbeat and a drop in blood pressure, hence this reduces the flow of blood to the brain. Attacks are often preceded by nausea, sweating, dizziness, and weakness, and are generally the result of stress, shock, pain, a stuffy atmosphere, or prolonged coughing. Fainting can also result from postural hypotension (low blood pressure), which can result from a person standing still for a long time or standing up very suddenly. This issue is common in elderly people, in those with diabetes mellitus, and in those taking antihypertensive drugs or vasodilator drugs.
In the majority of cases, recovery from fainting happens when usual blood flow to the brain is restored. This restoration often happens within minutes, because the loss of consciousness results in the person falling into a laying down positions, which then restores the flow of blood to the brain.