Humans really can sweat blood, new report finds

ITALIAN RESEARCH

glands known to cause “coloured sweat,” the doctors diagnosed hematohidrosis — a rare phenomenon that results in the “spontaneous discharge of ‘blood sweat.’”

There’s no one explanation for the source of the bleeding, the authors write. Others have hypothesized that capillary blood vessels feeding the sweat glands rupture, “causing them to exude blood” under conditions of extreme physical or emotional stress, another team reported in 2009 in the Indian Journal of Dermatology. “Acute fear and intense mental contemplation are the most frequent causes,” the authors of that report added, citing six cases of prisoners facing execution and another case during the 1941 London Blitz.

n the Italian case, the woman was treated with a beta blocker used for high blood pressure, which led “to a marked reduction, although not a complete remission of her bleeding.”

In an accompanying paper, hematologist and medical historian Dr. Jacalyn Duffin, of Queen’s University in Kingston, describes how Hungarian dermatologist Mortiz Kaposi defined hematohidrosis in 1895 as “the occasional spontaneous oozing of arterial blood from the sweat glands.”

However, standard hematology textbooks make no mention of it and Duffin said that none of the senior colleagues she asked had ever seen a case, “although two had witnessed bloody tears.”

Duffin said that while the condition is often traced by medical writers to the story of Christ’s suffering or the stigmata of St. Francis or Louise Lateau, hematohidrosis appeared in the scientific literature as early as the third century BC, when Aristotle described sweat that “either looked like, or really was, blood.”

In 1627, a Swiss doctor reported the case of a 12-yearold boy with a high fever who apparently sweated blood through his shirt.

When she searched the medical literature, Duffin found 42 published articles from 1880 to 2017, or an average rate of one every three years.

“Almost half the total output from more than a century came in the last five years,” with 28 new cases in peer-reviewed journals between 2004 and 2017.

Testing confirmed the presence of blood in every case. “In sum, clinical reports of true hematohidrosis persist at a steady and possibly rising rate," she said. Given the documented cases, “why — with all this evidence — do we still harbour doubts about its existence?”

“Ironically, for an increasingly secular world, the long-standing association of hematohidrosis with religious mystery may make its existence harder to accept,” she writes.

However, “it seems that humans do sweat blood, albeit far less often literally than metaphorically.”