LONDON (CNN) -- "Thanks for the nomination Luke," jokes a young man in a YouTube clip pouring what he says is a new, unopened bottle of Sambuca spirits into a pint glass along with another, unidentified drink. As the liquids mix, he observes: "And that is congealing nicely ... whew ... okay," before knocking back the potion.
After a brief pause he declares: "I nominate [he names some friends]. You've got 24 hours lads. Get it done."
The game, known as Neknominate, is thought to have originated in Australia and is now sweeping the world.
It involves you filming yourself downing a drink -- often alcoholic and of large quantities -- and then nominating a friend to outdo you. All this is posted on social media -- be it Facebook or YouTube.
But what started for some as fun has turned deadly; at least five men aged under 30 have died after drinking deadly cocktails. Now health professionals are warning young people of the risks of consuming large amounts of alcohol in a short time.
"This is a lethal game," Dr. Sarah Jarvis, medical adviser for the UK-based charity Drinkaware, told CNN. "The point about alcohol is that it affects your ability to recognize that you're in danger, and it absolutely affects your ability to react to danger. So we have a double whammy."
There appears to be no limit to the type of drinks that are consumed, and in what matter. Each nomination becomes more and more daring and outlandish.
It started as exhibitionism with this woman stripping in the supermarket and downing a drink, but the bravado has escalated into extreme cocktails:
One mixes spirits with a dead mouse, in another a man drinks out of a toilet, and the craze has seen players consume alcohol with goldfish, insects, engine oil and dog food.
Unsurprisingly the trend has prompted politicians to demand that schools play a bigger role.
"The Facebook drinking game Neknomination has gone viral, and very sadly young people have died as a result," said UK opposition spokesman Diana Johnson. "What role do schools have in building resilience in our young people to resist peer pressure?"
The role of social media giants like Facebook is also coming under scrutiny. Brian Viner, whose own son has played the game, demanded that those companies face up to their responsibilities.
His son was nominated and pressured to play the game but drank water instead of vodka so as not to harm himself.
"I was cross with him but more cross with the social media involved and the way this game has just spread," Viner said. "The whole thing is madness and it needs some kind of sharp and swift action on the part of these social networks to stop it."
Facebook said in a statement: "We do not tolerate content which is directly harmful, for example bullying, but behavior which some people may find offensive or controversial is not always necessarily against our rules.
"We encourage people to report things to us which they feel breaks our rules so we can review and take action on a case by case basis."
But Dr. Jarvis rejected this defense, saying Facebook must recognize its own role in the game.
"It's very difficult in this day of personal liberties to say that Facebook shouldn't be condoning this or taking these videos offline.
"Personally, I would like to see that happening. Frankly, if the thrill wasn't there, your mates weren't seeing you, I expect it would very rapidly fizzle out."
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