Chasing Life Why Seeing Blood Makes People Faint
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Oct 28, 2025 Discover why some people faint at the sight of blood, as Dr. Sanjay Gupta dives into the science of hemophobia. Learn about unique brain responses that differ from other phobias. Explore the genetic and evolutionary factors behind this fear. Plus, get the lowdown on artificial sweeteners, including their effects on health and microbiomes. Sanjay advises moderation and the benefits of whole foods as alternatives. Don't miss the tips on preventing fainting during blood draws!
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BII Triggers A Distinct Two-Phase Response
- Blood-injury-injection (BII) phobia triggers a unique two-phase response: a brief surge in heart rate and blood pressure followed by a sharp drop causing fainting.
- Brain scans show BII engages visual and attention areas rather than the amygdala, indicating different neural processing.
Hemophobia Activates Vision And Attention Centers
- fMRI research found spider-phobic brains light up the amygdala, but people with BII show more activity in visual and attention regions like the thalamus and occipital-temporal cortex.
- This suggests hemophobia is processed differently than other common phobias at the neural level.
Possible Genetic And Evolutionary Factors
- Genetics and sex may influence who develops hemophobia, with some studies finding higher prevalence in women.
- Fainting might be an evolutionary defense to restore brain blood flow after major blood loss, though this remains theoretical.