Misusing nitrous oxide can lead to life-threatening risks, a leading neurologist has warned, as Britain gears up to celebrate the new year.
The party drug, commonly known as laughing gas, is second to cannabis as the most commonly misused substance among 16 to 24-year-olds in England.
"I think it's wrong to call it laughing gas because that makes it seem like it's a joke," Dr David Nicholl, clinical lead for neurology at Sandwell and West Birmingham NHS Trust, told Sky News.
"It is a drug that is used as an anaesthetic, but that's with 50% oxygen in a supervised environment with health professionals who understand doses."
Acute exposure to the gas can lead to anaemia and nerve damage, and it has also been linked to fertility issues.
Dr Nicholl said misuse of the substance is currently the most common cause for emergency admissions to the neurology ward.
"People come into hospital off their legs, difficulty walking, presenting with tingling in the hands and feet, slurred speech and more rarely seizures.
"I've even spoken to one ophthalmologist colleague who has seen a patient who went blind, but that was secondary to hypoxia caused by inhaling nitrous oxide," he warned.
He said he had seen some users take canisters that are up to 3.9kgs in weight.
"If you took this in one sitting, it would kill you," he said.
Football coach Liam Cullen, 33, says he was addicted to nitrous oxide when he was in his 20s.
"I could go from anywhere between 12 and 18 hours a day, constantly doing balloons," he told Sky News.
"It changed my personality - I would be very snappy. I'm usually outgoing and a person that people like to be around. But when I was using nitrous oxide, I wasn't a nice person to be around."
'I couldn't feel my legs'
Liam would get through 600 canisters a day and says it left him in and out of hospital seeking medical help.
"I would have days that I had pins and needles and I just couldn't go into work, it was that painful. I couldn't feel my legs, couldn't feel the toes on my feet."
New data from N2O Know The Risks, a research project led by Queen Mary University, showed that while 91% of people had seen nitrous oxide canisters before, only 41% knew what they were.
And, 97% of those surveyed said they did not know inhaling nitrous oxide could damage the spinal cord.