A vasovagal reaction (also called vasovagal syncope) is sudden dizziness or fainting that can be triggered by pain, fright, or trauma. You may sweat, feel lightheaded, nauseated, or tingly, and you may pass out if the reaction continues.
A vasovagal reaction can happen without serious cause. But vasovagal reactions may be caused by heart problems, epilepsy, or other conditions that require treatment.
A vasovagal reaction can usually be relieved by lying down with your legs elevated. But treatment is necessary if a medical condition is causing the vasovagal reaction.