There's nothing worse than going for a nice, relaxing stroll in the sunshine only to accidentally walk right into someone's snot on the pavement.
It seems like 'snot rockets' are unavoidable at the moment, with a number of people feeling brazen enough to close one of their nostrils with a finger before blowing as hard as they can until a huge glob of snot shoots out right onto the floor below them.
But why on earth is this happening so much right now? Well, apparently, it's all to do with runners.
We've seen a surge in the popularity of running clubs as well as people documenting their lives through the running app Strava, and it turns out that this has had a direct impact on how much snot we're seeing in parks.
Any runners out there will no doubt know all about the 'snot rocket' phenonemon (Getty Stock Images) A 2017 study published in the International Journal of Otolaryngology found that between 27 and 74% of athletes struggle with rhinitis, which is the inflammation of the lining of the nose. It usually involves a blocked, runny or itchy nose and possibly bouts of sneezing.
Dr Adam Staten has commented on the phenomenon, explaining to the Metro that generating more snot than usual is a totally normal response from the body during intense exercise.
"When you exercise, your breathing speeds up due to an increased demand for oxygen, which causes you to pull a lot more air through your nose and airways," he said.
"The nose then warms and filters this air before it can reach the lungs, and mucus production is part of that process."
Dr Mohammed Ditta adds: "Non-allergic rhinitis, which is triggered by things like cold air, strong smells, pollution, or exercise, is frequently reported by women, although anyone can get it.
"If men seem more likely to do visible 'snot rockets', that is more plausibly down to behaviour, social norms, and exposure patterns rather than a biological factory making extra mucus."
Many runners deal with rhinitis on a regular basis (Getty Stock Images) Many offenders have even taken to social media admitting to 'snot rocketing' with one Reddit user confessing to 'shooting snot rockets' while running, poetically adding: "I am like a faucet that does not turn off until I’m finished running. I would love to find a way to spit less while running, as it’s a bit gross when running with new friends that aren’t used to it."
"If you meet someone who’s run a marathon," explained another. "They send that snot rocket, they wipe it on their clothes if need be. So if you want to run, you gotta be comfortable being gross."
Etiquette expert Laura Windsor has hit out over the rise of 'snot rockets', telling the Metro: "You should never do it in places where there are other people, first of all because it’s disgusting, and secondly because you’re making people feel uncomfortable.
"Etiquette is about making people around you feel comfortable. In a public space context, no, definitely not. No one wants to see you excreting mucus from your body."
Etiquette experts have called out the 'disgusting' habit (Getty Stock Images) Meanwhile, Jo Hayes, founder of EtiquetteExpert.org, recommends: "At the very least, remove yourself far from the sight/sound of any other human and deliver your snot rocket into a bush. "Ensure it hasn’t landed on a walking path, or anywhere other humans will be.
"Further, ensure there is no residual snot on your face or body. We’re humans, not animals. We have (most healthy people) control over our bodily excrements and can hold their release for appropriate situations.
"I’ll end with a reminder of the Golden Rule for life: do unto others as you would have them do unto you."