Do not upset U.S. teenager Calvino Inman too much - or he may see red. Doctors have been left baffled by the 15-year-old Tennessee teenager, who cries tears of blood.
They come three times a day, often without warning, and can last for up to an hour - leading some classmates to fear he is possessed.
Calvino and his mother have now appeared on national TV news programmes in the hope that exposure will bring an explanation to the stigmata-like medical mystery.
He said: 'Sometimes, I can feel it coming up, like a tear. I feel my eyes watering.
'Sometimes, it will burn as it comes out.'
Pictures and video show red teardrops rolling down his cheeks and leaving a bloody trail as his eyes brim with more blood.
So far, Tammy has taken Calvino for an MRI, ultrasounds, a CAT scan and to see several specialists. But as yet, none has been able to explain the medical mystery.
Ophthalmologist Dr Rex Hamilton said Calvino could be suffering from a rare condition known as haemolacria, which means 'bloody tears'.
'That is just a descriptive term of the manifestation of the bloody tears,' Hamilton told television show Good Morning America.
'It says nothing about what's causing that. It's a one-in-a-million kind of condition.'