(CNN) -- It begins with a nomination, from one internet user to another, to drink. But what started as a game, is now claiming lives.
Four victims, all men under 30, have died after playing the internet 'game' called neknominate. It's believed to have originated in Australia and is now in the United Kingdom and killed men in the Britain and Ireland.
The idea is that you nominate other internet users to 'nek', or down, a pint of alcoholic beverage, record yourself doing it, and then nominate others to get it do the same. The nominated person then has 24 hours to complete the task. If the nominated friend doesn't answer the challenge, they're ridiculed on social media.
Dr. Sarah Jarvis, is the Medical Advisor for Drinkaware, a British organization that provides alcohol education. She says the game has two side effects.
"This is a lethal game. 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," Dr. Jarvis said.
With each nomination comes bigger and more dangerous challenges.
It started as exhibitionism, with a woman stripping to her underwear in a supermarket and downing the drink. As the cocktails intensified, so too did the challenges.
One video posted online mixes a dead mouse in th drink. Another shows a man drinking out of a toilet while his friends hold him up.
Now, many are calling on Facebook to help put a stop to it. In some of the videos posted to the social site, ads are displayed next to it. Brian Viner, whose young son played the game but drink water instead of vodka, says Facebook needs to take responsibility.
"When you heard about your son taking part in this game how did you feel?
"Crossed with him but more crossed with the social media involved and the way this game has just spread. 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."
In a statement to CNN, Facebook said "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."
Dr. Jarvis says the social network can stop the game by recognizing its own role.
"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 happen. Frankly, if the thrill wasn't there, your mates weren't seeing you and I expect it would very rapidly fizz out."
A fleeting craze or a long-term trend, this is a game where no one wins.