Q. When I was a kid, I would get very bad nosebleeds. If nothing else worked, my mother would get out her keys and drop them down the back of my neck. I wish I knew why it worked it worked so well.
A. We have heard from many people who have had success stopping nosebleeds with keys or a cold butter knife against the back of the neck. We don’t know why this trick works, but one reader offered the following from his experience as a medic doing water rescue:
“The keys work because of the mammalian dive reflex. Cold hits the nerves in the neck, causing the blood vessels to constrict. You might notice your pulse slowing too.
“The dive reflex is why cold-water drowning victims are not usually pronounced dead until they are ‘warm and dead.’ Cold water only in the face/head area shunts blood to the organs and away from the skin and slows the metabolism for survival. The vital signs are often too weak to detect.”
This hypothesis sounds plausible to us. We can’t offer a better one.