A backpacker from Scotland recently found that the cause of her frequent nosebleeds was a 3-inch-long (7.5 centimeters) leech living inside her nose.
Twenty-four-year-old Daniela Liverani, of Edinburgh, had been traveling in Southeast Asia, and thought the nosebleeds were due to a motorbike crash she was involved in, she told the BBC.
The nosebleeds started when she was in Vietnam, and they persisted for a few weeks. The first time she went to a doctor because of the nosebleeds, she was told to come back if they continued, Liverani told BBC Radio Scotland.
What happened to Liverani is called hirudiniasis, a condition in which leeches (Hirudinea) attach themselves to a person's skin, or the inside of the mouth or nose. It's not known how commonly this happens to people, but there have been documented cases before, said Mark Siddall, a researcher at the American Museum of Natural History in New York.
Liverani said she could feel something moving inside her nose, but she thought it was a congealed blood clot.
"I didn't think it was a leech, obviously," she said. "That's not the first place your mind goes to when you have nosebleeds." [16 Oddest Medical Case Reports]
The leech may have gotten into Liverani's nose while she was swimming in Vietnam, or through her mouth as she was drinking water, Siddall said.
Siddall and his colleagues at The Leech Lab study the biodiversity of leeches, their habitat and their blood-feeding behavior. For example, they study the special anticoagulant proteins leeches produce in their salivary glands that "allow them to feed on blood without turning into a brick after ingesting so much of it," Siddall said.
Leeches can consume about five times their unfed body weight in blood, but they don't grow much in a single feeding, Siddall said. Liverani's leech was probably quite large even before it entered her nose, he said.
"They will grow very quickly when they are very young and very small — maybe doubling in size after two feedings — but this leech was probably not small when it entered," Siddall told Live Science.
It's not clear how it's possible not to notice such a large leech inside one's nose, but leeches are soft and very changeable in shape, so they can easily fit inside the nasal cavity. Siddall said he knows of several cases in which people were not initially aware of a leech in their nasal cavity, but eventually found out because of "a sliding sensation in their nose or persistent bleeding, or the leech peeking its head out."
As for Liverani, one day in the shower, the "blood clot" moved and came out just a little bit. "I had a proper look and saw ridges on it," Liverani said on the radio. "At that point, I realized it probably wasn't a nosebleed after all. It turned out it was a leech that has been there for about four weeks."
Once at the hospital, doctors removed the bloodsucking worm using forceps and tweezers.
"They were equally horrified and intrigued," Liverani said.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.