What is vasovagal syncope?

Common fainting: When the nerve vagus causes a fainting spell. Usually this happens in responds to a recent stimulus like when injecting needles, watching blood, during medical procedures, while fasting, while standing for long periods, while in fear or panic. When there is no other obvious cause for fainting it is said that is called "vasovagal syncope". There are other causes of syncope or loss of consciousness.

Mayo: According to mayo clinic vasovagal syncope is the most common cause of fainting. Vasovagal syncope occurs when your body overreacts to triggers, such as the sight of blood or extreme emotional distress. The trigger results in vasovagal syncope — a brief loss of consciousness caused by a sudden drop in your heart rate and blood pressure, which reduces blood flow to your brain.