It's turned up throughout history. Jesus was said to have been sweating blood before his crucifixion. The artist Leonardo da Vinci wrote about a soldier who had bloody sweat after battle.
Hematidrosis, or hematohidrosis, is a very rare medical condition that causes you to ooze or sweat blood from your skin when you're not cut or injured.
Only a few handfuls of hematidrosis cases were confirmed in medical studies in the 20th century.
People who have hematidrosis may sweat blood from their skin. It usually happens on or around the face, but the skin might be lining the inside of your body, too, like in your nose, mouth, or stomach. The skin around the bloody area may swell temporarily.
Hematidrosis can look like blood, bloody sweat, or sweat with droplets of blood in it. Sweating a different color -- like yellow, blue, green, or black -- is a different condition called chromhidrosis.
The bleeding usually stops on its own, and it's not serious, although it can make you dehydrated. And, of course, it can be disturbing.
Doctors don't know exactly what triggers hematidrosis, in part because it's so rare. They think it could be related to your body's "fight or flight" response.
Tiny blood vessels in the skin break open. The blood inside them may get squeezed out through sweat glands, or there might be unusual little pockets within the structure of your skin. These could collect the blood and let it leak into follicles (where the hair grows) or on to the skin's surface.
Who Gets It
It's also happened to women while they've had their periods.
Sometimes it seems to be caused by extreme distress or fear, such as facing death, torture, or severe ongoing abuse. It's probably where the term "sweating blood," meaning a great effort, comes from.
The doctor will ask you about the bleeding, including how long it lasts and when and how often it happens. They'll talk to you about your health in general, your medical problems, and the health history of close family members. They'll also want to know what's going on in your life.
To try to figure out what led to the hematidrosis, they may do blood and imaging tests to look for clues and rule out other problems. You'll probably get tests to check how well your liver and kidneys are working. You may have tests like a CT scan or ultrasound, depending on where the bleeding is.
Doctors who specialize in blood, skin, or other areas might get involved, too.
If the doctor finds or suspects that something is setting the hematidrosis off, they'll try to treat that underlying issue to prevent it from happening again. You may get: