Fainting: Vagal Reaction

Fainting (syncope) is a temporary loss of consciousness. It’s also called passing out. It occurs when blood flow to the brain is reduced. Your health care provider believes that your fainting was because of a vagal reaction. This is usually not a sign of serious disease.

A vagal reaction causes your pulse to slow down or the blood vessels to expand. This causes your blood pressure to fall. Less blood goes to your brain if you are standing or sitting. That results in dizziness, near-fainting, or fainting.

Common causes of fainting include sudden fear, severe pain, emotional stress, overexertion, overheating, quick movement or position changes, hunger, nausea or vomiting, and prolonged standing. Lying or sitting down right away and elevating your legs and feet can often stop the reaction before you pass out.