The death of a 47-year-old British man who suffered a severe nosebleed has medical examiners perplexed. Robert Ford of Gravesend, Kent, was walking with a friend when the nosebleed started, the U.K. Daily Mail reported today.

The bleeding was so severe that Ford went to a local medical center. After the bleeding stopped, doctors told Ford to go home and put ice on his nose. But hours later, he was dead.

An inquest into Ford’s death determined that blood had blocked his airways, causing suffocation. But how the blood got there — since the nosebleed had apparently stopped — is a mystery.

“This was certainly an odd case,” Dr. Olaf Biedrzycki, a pathologist who testified at the inquest, told the Daily Mail. “We don’t really know how to explain it. I’ve looked very hard for a source of the blood and could not find it.”

Ford’s father, Michael, called 911 after finding his son on the floor with a pool of blood around his mouth, according to the Daily Mail. There were also dime-sized spots of blood throughout the house.

The coroner ruled the death a result of natural causes.

The lining of the nose contains tiny blood vessels that can rupture when dry or irritated. Cold weather, a scratch, certain chemicals and allergies can trigger bleeding.

“We see an increased frequency of nosebleeds as the weather turns cooler because people start heating their homes,” said  Dr. Jason Homme, assistant professor of pediatrics at the Mayo Clinic. “When the humidity goes down, the nasal lining is drier and more prone to irritation.”

In children, Homme said, the commonest cause of nosebleeds is digital trauma — nose picking.

Most nosebleeds aren’t serious. But in rare instances, they can signal more serious problems like bleeding disorders.

“If the bleeding lasts for more than several minutes with direct pressure, or if you have difficulty breathing, then you need to see a doctor,” said Homme. “And if you have chronic nosebleeds and any other signs or symptoms of a bleeding disorder, like easy bruising or bleeding gums, or a family history of bleeding or clotting problems, you want to see someone.”

Nosebleeds resulting from trauma, such as a sports injury or a car accident, should also be examined by a physician.

“Any time there’s profuse bleeding, it’s best not to try and take care of it yourself,” said Homme. “Have someone drive you in; don’t try to drive.”