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A portrait of Vlad III, or "Vlad the Impaler", Prince of Wallachia from 1456 to 1462, thought to be the inspiration for the fictional Dracula.

Bram Stoker’s Dracula was known for drinking the blood of his victims, but it turns out that the 15th-century warlord considered to be the inspiration for the vampire may have cried blood.

Scientists in Italy and Israel have analysed specks of biological material left on three letters written by Vlad the Impaler, which suggest that the real Dracula might have suffered from a condition known as hemolacria, which would cause his tears to be mixed with blood1.

Vlad III, also known as Vlad Drăculea (Son of the Dragon) – was a prince and military ruler of the Wallachia region in southern Romania. He fiercely defended the area from armies of the powerful Ottoman Empire — reputedly killing more than 80,000 people during his lifetime.

Vincenzo Cunsolo, of the University of Catania, and colleagues in Catania, Milan and Rehovot in Israel, along with Tudor Arhire of the Romanian National Archives, studied three letters written, signed and sent by Vlad III to the rulers of the city of Sibiu – one in 1457 and two in 1475. The researchers placed non-invasive plastic film on the letters to extract the components of proteins known as peptides, which they identified using high-resolution mass spectroscopy.

The team carried out a series of tests to distinguish peptides deposited when the letter was written from other molecules introduced later. One test measured deamidation, a natural modification of two specific amino acids that can act like a marker of protein ageing.

That process yielded 16 human proteins that the researchers are confident were originally on the letters – their lab analysis having identified at least two of the peptides making up each protein. Some of these proteins are related to the skin, while others relate to breathing and retinal diseases. Other proteins are found in the blood, including one which is also involved in tear-making.

It was this latter finding, in part, which led Cunsolo and co-workers to conclude that Dracula may have cried tears of blood – which would be consistent with some historical accounts. They also found indications that he might have developed his affliction as he got older, as retina- and tear-related peptides were found only on the later letters.

The researchers also found large numbers of peptides from other living organisms. As they point out, Wallachia was a busy crossroads for merchants, slaves and soldiers, and perhaps also for disease. Among the many bacterial peptides that they found were those from the group Enterobacterales, which includes the pathogen responsible for the 14th-century Black Death.