If you haven't yet taken the ice bucket challenge, the chances are the dreaded nomination is creeping ever closer through social media as, one by one, distant acquaintances and friends succumb.
However, the American medical charity behind the craze, the ALS Association (Alsa), has angered rivals by attempting to trademark the fundraising gimmick – the idea of someone dumping a bucket of freezing water and ice over their head – and is under pressure to say what it will do with the vast amount of money it has raised.
Alsa funds research into amyotrophic lateral sclerosis (ALS), known as motor neurone disease in the UK, and its income has risen from $24m (£15m) for the whole of last year to more than $100m in the past four weeks alone.
In pictures: The famous do the ice bucket challenge
In pictures: The famous do the ice bucket challenge
1/16 Lady Gaga
Lady Gaga managed to keep an admirably straight face as she poured what looked like a solid silver bowl of cold water over herself
2/16 Homer Simpson
Fans were overjoyed when their favourite yellow cartoon character got involved in the campaign to raise money to help those suffering from ALS. As per usual with Homer Simpson, things escalated quickly
3/16 Reece Witherspoon
One of those who have arrived slightly late on the scene, actress Reece Witherspoon looks nervous but resolute as she has a bucket of ice-cold water chucked over her head
4/16 Lily Allen
Lily wore a bikini as she self-administered her bucket of icy water. She thanked Jess Glynne for the nomination, and passed the challenge onto Mark Ronson, Millie Mackintosh and rapper Giggs
5/16 Daisy Lowe
Celebrity ALS Ice Bucket Challenge videos seem to be coming in faster than we can watch them - model Daisy Lowe is one of the most recent to get involved. She was nominated by Sun journalist Dan Wooton, and passed it on to radio presenter Nick Grimshaw and Abbey Clancy
6/16 Bill Gates
One of the first to go viral on YouTube, Bill Gates had freezing water tipped over him in a bid to raise millions of dollars to fight the illness ALS
7/16 George W. Bush
It felt like quite an important moment when the former President of the United States accepted nominations from his daughter Jenna Bush Hager, golfing champion Rory McIlroy, Woody Johnson, and Jim Harbaugh. He nominated 'my friend Bill Clinton'
8/16 Jimmy Fallon
In an official letter this week, the ALS Association said: 'Never before have been in a better position to fuel our fight against this disease.'
NBCU Photo Bank via Getty Images
9/16 Tom Hiddleston
Amyotrophic lateral sclerosis affects the brain and the spinal cord. Motor neurons degenerate and die which makes it increasingly difficult to move muscles
10/16 Rita Ora
There is no known cause of ALS, though there is a proven hereditary factor in some cases
11/16 Taylor Swift
There is also no known cure, though the millions being raised by the ALS association will go towards researching these great unknowns
12/16 Oprah Winfrey
The illness is also known as Lou Gehrig’s Disease, named after the all-time great baseball player from the early 20th Century whose time at the top ended when he was stricken with the illness in 1939
13/16 Mark Zuckerberg
The Facebook founder is unarguably the master of the challenge, who – following his drenching – saunters off
14/16 Justin Bieber
Bieber's first attempt was pretty naff: he didn’t quite get it and decided not to use ice or a bucket to complete the challenge. Obviously, the internet moaned at him and he was brilliantly peer pressured into having another go
15/16 Justin Timberlake
Celebrities have been nominating one another to do the challenge
16/16 Christiano Ronaldo and Marcelo
The challenge is now making its way over to this side of the Atlantic, former Manchester United players Paul Scholes and Gary Neville both doused themselves in cold water for a terminally ill fan
But its attempt to commercialise the phrase "ice bucket challenge" – it lodged a trademark application with the United States Patent office last week – may have backfired. Others in the charity community are now demanding to know how the new money will be spent.
A lawyer for a leading US charity, who asked not to be named, said: "Alsa tried to freeze us out and make a fortune out of an idea that will become as commonplace as a fun run or a charity cycle. So naturally there's a bit of pay-back. They've brought this attention on themselves."
Alsa said the flood of "ice bucket" money would not be held back "for a rainy day" or put into a long-term endowment fund. It pledged it would be spent on research into ALS – commonly known in the US as Lou Gehrig's disease after the baseball player who revealed in 1939 that he was suffering from the disease.
Last year, Alsa spent 18 per cent of its revenue on administration and other fundraising costs. A statement of its "functional expenses" lodged with the Harrington Group of accountants stated that salaries, research, travel, conference fees and equipment purchases were among the $3.6m it spent from its donations. It remains to be seen how much the expenses bill will rise, if at all, as a result of the extra donations.
What began on US TV channels, focusing mainly on sports stars, quickly spread to everyone from the former US president George W Bush and Scotland's First Minister, Alex Salmond, to the singer Kylie Minogue, the actor Benedict Cumberbatch and the model Kate Moss. Barack Obama and David Cameron have been challenged but have so far refused, although both made donations.
However, the attempt to trademark the stunt hit a sour note even though two applications filed to protect the phrase "ice bucket challenge" were quickly withdrawn.
The US charity community – and its legal advisers – complained that if the patent application was successful, other charities who attempted to hold similar events would have had to pay Alsa a percentage of any money they raised.
They also pointed out that fundraisers involving a "cold water challenge" and other ice plunges had taken place in New Zealand and in the US before Alsa's campaign went viral this summer.
One legal argument sent to the US Patent Office pointed out that almost three quarters of all charity fund-raisers in the US and in other Western countries, involved running but no one had tried to own the phrases "fun run" or "charity run".
The UK equivalent of Alsa, the Motor Neurone Disease Association, defended the US association and criticised the Macmillan Cancer Support charity for announcing its own ice bucket challenge event. MNDA supporters accused Macmillan of attempting to hijack a successful fundraising idea, saying it would dilute the overall attempt to increase awareness of MND.
After the deluge...
After the deluge...
How charities are competing with the ice bucket challenge:
* Macmillan Cancer Support is challenging men and women to "Shave or Style" their hair and donate £3 by texting STYLE to 70550
* For the testicular cancer charity Check One Two you can take a compromising or funny picture of yourself on social media and send the picture to #FeelingNuts
* For the 12th year in a row, Japanese porn stars are offering their services in conjunction with The Japan Foundation for Aids Prevention. Nicknamed "Boob Aid", donations are made in exchange for fondling the models' breasts.