Humans really can sweat blood, report finds
Humans can literally sweat blood, doctors and medical historians are reporting in this week’s issue of the Canadian Medical Association Journal.
In a brief case report, Italian doctors describe a 21-year-old woman with a three-year history of spontaneous and “self-limited” bouts of bleeding from her palms and face through perfectly intact skin.
“There was no obvious trigger for the bleeding, which could occur while she was asleep and during times of physical activity,” researchers from the University of Florence write.
The bleeding episodes lasted one to five minutes and were more intense whenever the woman was feeling emotionally stressed. Embarrassed by the bleeding, the woman grew isolated, depressed and anxious.
“During admission, we observed the discharge of blood-stained fluid from her face,” the authors write. There were no obvious cuts in her skin. After ruling out conditions like chromhidrosis, a disorder of the sweat 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.
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.”