'Hippy crack': why is nitrous oxide popular despite the risks?

More than 3,500 canisters of nitrous oxide – also known as hippy crack or laughing gas – were seized by police at Notting Hill Carnival this weekend.

Scotland Yard said the canisters had a street value of more than £17,000.

The use of the recreational drug is on the rise, with users reporting a brief but intense high that makes them feel euphoric, relaxed and giggly. Deaths are rare, but at least 17 people in the UK died after breathing in the laughing gas between 2006 and 2012.

The London Ambulance Service issued an alert ahead of this year's Notting Hill Carnival after numerous people required emergency treatment at the event last year.

Paul Gibson, LAS tactical commander for the carnival, said legal highs had posed a "big problem" for the ambulance service last August.

"We treated many people who presented symptoms having taken legal highs," he said. "These included seizures, falls and people suffering injuries as a result of assaults."

The warning comes after a London teenager died in July after allegedly inhaling the popular drug. Ally Calvert, an 18-year old from Bexley, was rushed to hospital when he collapsed outside a block of flats one Saturday night. He went into cardiac arrest and was pronounced dead on the way to hospital.

Police believe he may have been inhaling the legal high as well as drinking alcohol at a party in south-east London. His death is currently being treated as "unexplained" until the results of the post-mortem are released.

Mixing nitrous oxide with alcohol is especially dangerous as it can increase the dangers associated with both substances and can lead to an increased risk of accidents or death, according to the national drug education service Frank.

More than 500,000 young people took 'hippy crack' last year, making it second only to cannabis as the most popular drug for people aged between 16 and 24. Even Prince Harry is alleged to have tried it in 2010. But what exactly does it do and how dangerous is it?

What is hippy crack?

Hippy crack is nitrous oxide, also known as laughing gas. It has become a craze at festivals and concerts, where it can often be bought in balloons to inhale for £2 or less. It works by blocking signals to the conscious mind from other parts of the brain, giving users a brief feeling of intense euphoria and relaxation. The gas was traditionally used by dentists and surgeons to numb pain and is put into some aerosol cans as a whipping agent, as in whipped cream canisters.

Is it legal?

Nationally, possessing and inhaling nitrous oxide is legal, but supplying it to under-18s could lead to prosecution. Unlicensed vendors risk a two-year prison sentence. Driving under the influence of nitrous oxide could also lead to a heavy fine, disqualification from driving and even a prison sentence.

Locally, councils are cracking down on the stimulant. In August, Lambeth Council became the first local authority in the country to ban the use of nitrous oxide. Users within the council's boundaries face a £1,000 fine under a dedicated Public Spaces Protection Order. The council said it hoped the ban would reduce anti-social behaviour and the number of small metal canisters littering the streets.

Jane Edbrooke, Lambeth Council's neighbourhoods' chief, says they have been inundated with complaints from residents about laughing gas in the borough over the last year. "Legal highs are simply not safe. It is our duty to keep our residents safe and this new order should deter people from supplying and using legal highs in the borough," she said. "The litter and anti-social behaviour associated with certain legal highs have also blighted areas like Vauxhall and Clapham and now we have the power to do something about it."

How did hippy crack get its name?

Hippy Crack is considered to be more of a tongue-in-cheek name than actually having any relation to crack cocaine. However, the short length of the high and eagerness of some users to keep going back for more are said to be similar. The term has been around for years, although nitrous oxide has also been referred to as nitrous, balloons, N2O and sweet air.

Is it dangerous? 

Short-term side effects can include headaches, dizziness and unconsciousness, while long-term, excessive use has been associated with anaemia, incontinence, depleted bone marrow and numbness in fingers and toes. The recreational use of nitrous oxide can be fatal, but deaths are rare. In some fatal cases, the person has put a bag over their head to inhale it or opened a tank in a sealed space, such as a car. Joseph Benett, a 17-year-old art student from north London, suffered a cardiac arrest, fell into a coma and died after inhaling the gas in 2012. An interim Hertfordshire Coroner's Court report gave the cause of death as hypoxic brain injury caused by inhalation of nitrous oxide. In March this year, a 22-year-old University of Brighton student was found dead with about 200 spent canisters in his room. An inquest found his death was caused by asphyxiation as a result of the chronic use of nitrous oxide gas. Before his death, he was said to have had such chronic nerve pain that he could not walk down stairs.

How does hippy crack compare to other drugs?

Last year, nitrous oxide was the 14th most used drug worldwide, according to the Global Drugs survey 2014. Some experts believe it may be a relatively low-risk drug compared with other intoxicants in the top 20, The Independent reports. Alistair Bohm of Addaction, the UK's largest drugs and alcohol charity, said: "We can't credibly deny that compared to other drugs it is relatively low risk."

He added: "The risks from taking it from balloons are quite low. When there have been stories about deaths, they tend to be from people who are using canisters and masks, then you get into the dangers of asphyxiation."

How common is hippy crack in the UK?

Around 7.6 per cent of people aged 16 to 24 in England and Wales have taken nitrous oxide, according to Home Office Drugs Misuse data collected in 2014.

Last year approximately half a million young people were thought to be frequent users of the gas, according to the Local Government Association, which represents 400 councils around the country. In the past few years, hippy crack has become a popular drug at music festivals, the Independent says.

Nitrous oxide was included on Glastonbury's list of "what not to bring" this year. Organisers also issued a warning to say that it would not be welcome in the King's Meadow, known as the festival's Sacred Space, after two tonnes of canisters had to be picked up by hand last year. The area has "lost its way", said co-ordinator Liz Eliot. "It's become known as a place where people take nitrous oxide, a damaging drug which pollutes our beautiful field with noise, litter and N2O gas (a greenhouse gas which is 298 times more polluting than carbon dioxide). Nitrous oxide is also dangerous: an exploding canister was the source of a major injury at last year's Glastonbury." Nevertheless, dozens of revellers were spotted inhaling substance from balloons when the festival took place in June.