Anatomy Of A Hot Flash

Here’s the biological wiring that switches on the sudden sweats.

By Sharon Kay

Here’s The Breakdown of Your Hot Flashes



Portions of the brain, which control body temperature, react to dips in the blood level of hormones.


The brain’s insular cortex, which controls perceptions of heat, cold, pain and pleasure, turns on.


About 20 minutes before a full blown hot flash, your core body temperature begins to rise.


About 10 minutes before a flash, skin temperature rises. Vessels dilate and blood flow increases to prepare the body to get rid of the extra heat.


An aura—dizziness, a racing heart and a sense of anxiety or unease—may also precede a flash.


You feel hot, sometimes intensely, mostly on the upper third of your body.


Sweat glands prepare to start pumping out perspiration.


Blood rushes to skin across your chest, neck and face, causing flushing.


You begin to sweat, mostly on the upper part of your body.


Peripheral blood vessels, in your arms, torso, legs and face, fully dilate, and heat shoots out.


Total time of thermal chaos: under five minutes. Flashes are most common in the morning and evening, according to researcher Robert Freeman of Wayne State University.

Originally published in More magazine, December 2005 / January 2006.

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