Graphic designer Phil Lyndon, 52, was suffering from a persistent cough and, one day, he needed to spit up what felt like a huge phlegm wad.
Unfortunately, it was something much more unsightly.
When he eventually relieved himself, Lyndon coughed up a 5mm bug; more specifically, a mayfly nymph.
Upon closer inspection - when staring down into the toilet - the "phlegm wad" was moving.
Lyndon, who lives in Ealing, west London, had been prescribed antibiotics to treat his congestion, but the meds did not work.
"It (the bug) had stopped moving by this point and I took a picture of it on my iPad. When I zoomed into the image I could clearly see that it was a bug. I was alarmed that there might have been something alive inside my lungs and knew instantly that it was not something I could ignore."
Lyndon went back to his regular physician, who then referred him to University College London's Hospital for Tropical Diseases, according to the Daily Mail.
Doctors x-rayed his chest to check for an "infestation," and took a blood test. There were no changes caused by the creature, and the results came back clear.
The bug was collected to be examined by an expert, and Lyndon emailed a picture to the British Bugs project.
An expert from the website informed him that it looked like a mayfly nymph, missing most of its legs, and was "definitely not anything parasitic," the Daily Mail reported.
"More likely you accidentally ingested it sometime, perhaps while asleep - they'll be coming out of water to emerge as adults around now, and sometimes end up on people's ceilings," the organization said.
"I uploaded a picture of the bug to the Northfields Friends Facebook group and have since had over 130 comments from concerned friends, some of whom expressed complete horror at what I had coughed up," Lyndon said.
