Hematidrosis is the rare condition where a human will actually sweat blood.  This can be a response to extremely stressful or terrifying situations.  In these situations, the blood vessels that surround the sweat gland dilate to the point of rupture, and the blood actually runs into the sweat gland and out of the skin.

It kind of looks like a Gatorade commercial.

And it’s pretty badass.

Until it happens to you.  And you get disgusting pit stains.