The vampires on HBO's hit series True Blood do it all the time. They get angry or sad and blood streams down their faces instead of clear tears. But when it happens to humans in real life, it makes for a medical mystery that doctors have been trying to solve for decades.

Twenty-year-old Yaritza Oliva began inexplicably bleeding from her eyes earlier this month. Doctors ruled out conjunctivitis and eye infections, but still prescribed eye drops to ease Oliva's pain. According to the Huffington Post, the Chilean woman baffled doctors, who now believe that she suffers from a rare condition called haemolacria.

Haemolacria is a condition that causes blood to either tinge a person's tears or become the entire composition of tears. Doctors neither know of a cause nor an effective treatment for the condition. Many do believe, however, that haemolacria is a symptom of blood-related diseases and tumors.

Very few people in history have had haemolacria and doctors have not yet diagnosed Oliva with the condition. The young woman and her family expressed that they do not have the financial resources to go to a specialist who could possibly determine the cause of the bleeding. They have asked the public to donate funds.

"Nobody knows what to give me, they don't know what I have," said Oliva. "They don't know what to do."

The only known case of haemolacria in the United States was in 2009. Calvino Inman, a 15-year-old from Tennessee, said that he cried tears of blood at least three times a day without warning. "Sometimes, I can feel it coming up like a tear. I feel my eyes watering," said Inman. "Sometimes it burns when it comes out." Four years later, there's still no word that Inman has found an effective treatment for his condition.