An Italian woman was hospitalized after “sweating” blood from her face and palms–an extremely rare condition that’s left doctors puzzled.

“There was no obvious trigger for the bleeding, which could occur while she was asleep and during times of physical activity. She stated that more intense bleeding occurred during times of perceived emotional stress. Episodes lasted from one to five minutes,” the report stated.

The woman became “socially isolated” due to the problem, the researchers said, while adding that she also suffered “major depressive disorder” and panic disorder as a result.

Dr. Jacalyn Duffin, who is a medical historian and hematologist at Queen’s University in Kingston, Ontario, wrote a commentary on the report, noting that the “sweating blood” condition has been reported for centuries, according to LiveScience.

The woman likely suffers from hematohidrosis. No one knows how the condition is caused.

“In the literature, there is no single explanation of the source of bleeding in hematohidrosis. Despite the fluid’s sweat-like appearance, the hypothesis that blood passes through eccrine ducts, induced by abnormal constrictions and expansions of periglandular vessels, has not yet been proven,” CMAJ said.

“Bleeding has also reportedly occurred through areas without sweat glands,” it added, “or through the follicles.”

“The presence of dermal defects leading to blood-filled spaces exuding via follicular openings or directly into the skin surface has also been proposed,” the report said.

In May, another, similar case was reported in Thailand.

Phakamad Sangchai from Nongkghai, Thailand, starts bleeding from her nose, eyes, and skin every time she gets a headache.