How can the sight of blood cause someone to pass out?

Question

I understand that loss of blood pressure and oxygen to the brain can cause one to pass out, but how can the sight of something like blood cause it?

In: Biology

Answer 1

Answer: If someone has a phobia of blood, when they see it, most likely the body’s “fight or flight” response starts up. The persons heart rate goes up, sometimes accompanied by hyperventilation, they feel sweaty and they freeze up. Occasionally they may also pass out, which answers why someone might pass out at the sight of blood.