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By Mayo Clinic staffVasovagal syncope is the most common cause of fainting. It occurs when your body reacts in an exaggerated way to such triggers as the sight of blood or extreme emotional distress. The trigger results in a sudden drop in your heart rate and blood pressure, which reduces blood flow to your brain and causes you to briefly lose consciousness.
Vasovagal syncope is usually harmless and requires no treatment. But your doctor may recommend tests to rule out more-serious causes of fainting, such as heart disorders.
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