Why do your eyes go red when you cry?

THAT’S THE WHY: Maybe you didn’t get the Valentine’s card you really wanted yesterday

THAT'S THE WHY:Maybe you didn't get the Valentine's card you really wanted yesterday. Maybe you're going through a break-up, you've been turned down for a job or you've just had a really bad day.

Sometimes a good cry can help let it all out, but why when you’ve had a big blub do your eyes give the game away by turning all red and blotchy?

The “Ask a Scientist” section on the Howard Hughes Medical Institute website (hhmi.org) offers an explanation from Prof Jeremy Tuttle at the University of Virginia Health System’s department of neuroscience.

When you are using your eyes for seeing and not crying, the blood vessels that deliver oxygen and nutrients to those tissues are not dilated and so are almost invisible, he explains.

When you cry though, the lacrimal glands close to your eyes pump out secretions. These glands normally function to help keep your eyes moist.

But when a bawl is required, the blood vessels that service the glands dilate to supply them as they go into overdrive, and we can start to see the redness.

“When you cry, the fluid making up the tears has to come from somewhere; it is derived from the blood supply to the glands. Therefore, when you cry, the blood vessels to the glands have to dilate to provide the fluid for the tears,” states Prof Tuttle.

“If the crying is intense enough, the blood vessels on the surface of the eye also dilate. Voilà!”

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