The White Rhino took to social media on Sunday morning to reveal his shock decision – stating he ‘‘doesn’t want to get punched any more” and wants to spend his time “getting nice and fat".
Allen ends with a record of 18 wins, five defeats and two draws.
He had been due to appear on the Conor Benn versus Sebastian Formella bill next Saturday but has hung up his gloves with immediate effect.
Allen’s humour and lighthearted antics – including a visit to the Babestation studios and stuffing a sock down his pants during his weigh-in for his fight against David Howe – made him a cult figure among boxing fans.
He also won plenty of admirers for opening up about his mental health issues, including battling depression, a gambling addiction and his struggles with training and diet.
Allen wrote on Instagram: “Hello everyone, I hoped I would never have to write this message, never mind at 28 with my last fight being when I was 27 years old.
“But I made the decision a few nights ago with my sister that I would no longer from that moment on be a professional fighter.
“Boxing has given me a life I could never have dreamed of.
“I had never been out of Doncaster but for school trips until I started boxing and it’s taken me round the world from New York City to working men’s club all around the UK.
“As well as seeing the world it has taken me from the kid brought up in a council house with yellow doors wearing Umbro to a man who still wears Umbro but owns a few houses and who has given myself a chance to give my future kids a life I could only have dreamed of.
“On top of [that], and more importantly, I have made the greatest friends, some of them being my childhood heroes.
“The list of thanks would be far too long but I hope everyone knows who they are and know they are appreciated.
“Lastly, the reason for me calling it a day is simple – I don’t want to get punched any more.
“Long gone are the days of the kid from Donny who just wants to fight.
“All I want now is a nice quiet life with a wife and some kids, healthy and happy, getting nice and fat.”
Allen’s career peaked in April last year when he knocked out former WBA champion Lucas Browne at The O2.
But just three months later he required hospital treatment after a punishing knockout defeat to David Price.
He shared the ring with big-hitters Dillian Whyte, Luis Ortiz and Tony Yoka.
Allen had been due to fight Christopher Lovejoy on the undercard of Oleksandr Usyk versus Derek Chisora on Halloween night but it was cancelled due to a contractual issue involving Lovejoy.