You may have heard the idiom "We sweated blood", but it turns out that it's a real medical condition and can actually happen, as demonstrated by the case of a 21-year-old woman in Italy.

According to her doctors, she came to the hospital reporting incidents where she'd bleed from her face and hands, without any evidence of injuries or other obvious triggers, going back three years. Tests confirmed that the fluid was blood.

The cause? A rare and puzzling condition called hematohidrosis.

Cases of the condition date back millennia, as early as the third century BCE, in treatises by Aristotle. It's said Jesus of Nazarus sweated blood the night before his execution, and Leonard da Vinci reported a case of a soldier who sweated blood before battle.

In 1996, a pair of physicians presented a classification based on 76 cases from the 17th century to 1980.

However, until fairly recently, medical science on the condition has remained noncommittal, according to Jacalyn Duffin, who penned an additional report to accompany the case report. In fact, as late as 2012, the Elsevier Textbook of Dermatology noted that hematohidrosis had not been confirmed by science.

There have been more recent cases. Researchers and doctors have submitted reports of a 72-year-old-man with the condition in 2009, a 13-year-old boy in 2010, an 18-year-old woman and 12-year-old girl in 2013.

For her History and Review article, Duffin looked at 28 such case reports between 2004 and 2017.

"In sum, clinical reports of true hematohidrosis persist at a steady and possibly rising rate," she concluded. "This collection of well-documented observations commands respect and acceptance."

This is important, too: no one knows what causes the condition. More than one researcher has suggested that it may have something to do with emotional distress, but it's possible that only by taking it seriously, carefully documenting each case and studying them that we may approach an answer.

The 21-year-old patient's case is consistent with previous cases. She reported that her bleeding could occur at any time, even when she was asleep, lasting from one to five minutes. She also said that it was more intense when she was emotionally distressed.

As a result, her social life had suffered. She had isolated herself because of the embarrassment of the condition, and reported symptoms consistent with depression and panic disorder.

The doctors found no evidence to suggest that the condition was made up. They treated her with medication for her depression, and high blood pressure medication that has been used to treat previous cases of hematohidrosis.

Although her condition has improved, they said, the bleeding has not stopped entirely.

The case was reported in the Canadian Medical Association Journal.