Go on, eat that mishandled roast beef sammy, t'aint gonna hurt none …

You're dirty. Your mom is dirty. All your friends are dirty and that dog you own is dirty too. That's just the way the world is: We're filthy creatures living in a disgusting place with bacteria, germs and whatever else thriving all around us. 

But what makes something so full of ick that you'd refuse to eat it? Generally, this can be explained by the storied '5 Second Rule' — or how long you have to pick something up off the ground before it's not safe to eat anymore. It's a tried and true mantra spoken by everyone for the past millennia. Through its life, it's been challenged, mocked and continually refuted. But not anymore. Now, the 5 Second Rule is finding vindication through one germ expert — a professor from Aston University in Birmingham, UK — who suggests picking up dropped food is fine. 

Anthony Hilton will be demonstrating how this all works at The Big Bang Fair (a celebration of science, technology, engineering and maths for young people) this week in Birmingham.

He claims eating stuff off the floor doesn't come without dangers, of course, but you're probably pretty safe.

"Eating food that has spent a few moments on the floor can never be entirely risk-free," says Hilton. "Obviously, food covered in visible dirt shouldn't be eaten, but as long as it's not obviously contaminated, the science shows that food is unlikely to have picked up harmful bacteria from a few seconds spent on an indoor floor."

Though, that isn't to suggest germs won't go from the floor to your mishandled roast beef sammy, he says. But it's not as bad as some people would lead you to believe.

"Our research has shown that the nature of the floor surface, the type of food dropped on the floor and the length of time it spends on the floor can all have an impact on the number that can transfer," he adds.

Even still, germs aren't all bad for humans. It's how we build an immune system after all, when our bodies are forced to fight off infections. And there are even good bacteria living inside of you right now, too, that aid in digestion and keeps you company at night when your dirty dog decides to sleep in the kitchen. 

Why put blind faith in a man you haven't met who says he's cracked out one of the oldest known wives' tales to ever exist? Confirmation bias, probably — but also because you spent a lot of money on that sandwich and it's criminal to let it go to waste just because you dropped it. 

Five Second Rule for the win.