The deadly rise of 'hippy crack': For celebrities, it's the party drug du jour. Now inhaling laughing gas - is spreading to middle-class living rooms

Coronation Street actress Michelle Keegan has been spotted taking the drug

Even Prince Harry was seen indulging in nitrous oxide two years ago

Effects can cause strokes, hallucinations, seizures, blackouts, incontinence, stress on the heart

Such is the ease of availability that it has even infiltrated middle-class living rooms

Her eyes shining with anticipation, the young woman holds a balloon to her lips. For all the world, it looks as if she's about to perform a children's party trick.

Yet a quick examination of her surroundings (an expensive London nightclub) and her appearance (glossy hair, designer heels) tells you that this is far from a children's party.

Indeed, the young woman is something of a celebrity — Coronation Street actress Michelle Keegan. And far from performing a trick, she is indulging in a fashionable — and potentially fatal — drug craze: inhaling nitrous oxide, the 'legal high' du jour.

Dangerous: Coronation Street actress Michelle Keegan indulging in a fashionable ¿ and potentially fatal ¿ drug craze: inhaling nitrous oxide, the 'legal high' known as 'hippy crack'

Cheap, seemingly harmless and guaranteeing a night of raucous laughter, so-called 'hippy crack' is increasingly popular with celebrities and their well-heeled young fans alike. Even Prince Harry was seen indulging two years ago.

There is just one problem: nitrous oxide is no more legal than it is innocuous. Despite being touted openly at music festivals and in bars and nightclubs across the country, sale of the gas for recreational use is very much against the law.

As for being innocuous, that is only true if one ignores the alarming side-effects it can cause: strokes, hallucinations, seizures, blackouts, incontinence, stress on the heart, chronic depression and even — in cases of prolonged use — depleted bone marrow. Few would tack the word 'harmless' on to such a list.

Now anti-drugs campaigners are calling for more to be done to tackle the trend. Not that their voices are being heard, swamped as they are by those of the enthusiasts. In the past month alone, several minor — yet influential — celebrities have jumped on the bandwagon.

As well as Keegan, James Argent and Maria Fowler, stars of The Only Way Is Essex, have been pictured with a balloon between their lips.

They are among tens of thousands of young people who have dabbled with the drug. And, as it sells at the bargain price of £1.50 per balloon, many indulge in it every weekend.

Nitrous oxide — also known as laughing gas, N2O and sweet air — gives users an intense euphoria which some have likened to the effects of heroin and crack cocaine.

Aficionados insist this is a huge exaggeration, and maintain that it is far less harmful than other illegal drugs — indeed vastly preferable to alcohol, as the effect recedes in minutes and there is no hangover.

Ask the experts, however, and they tell a very different story. When inhaled, nitrous oxide dissolves in the bloodstream, depleting the blood of oxygen and reducing its flow to the brain and other vital organs. An overdose can be fatal.

Stephen Ream, director of substance abuse charity Re-Solv, is unequivocal: 'Every year, people die in this country from taking nitrous oxide. You never hear about that when people are selling it in nightclubs or at festivals, and I shouldn't imagine most of the users even realise it's illegal. It's almost the acceptable face of drug abuse.

Problem: Ruby Deevoy says her overindulgence with nitrous oxide led her to suffer severe hallucinations

'Young people see celebrities taking it and they think it must be OK, but they should be looking at Demi Moore and what happened to her.'

Unlike the British C-listers associated with the drug, Moore is a bona-fide star, and her experience is very much a cautionary tale.

Earlier this year, in the throes of a difficult separation from her husband, Ashton Kutcher, the actress reportedly binged on nitrous oxide to the extent that she suffered a seizure and had to be taken to hospital. She then checked into a rehabilitation clinic.

Yet little was reported about the drug — it was lost in the controversy about Moore's romantic travails and alarming weight loss.

Small wonder, then, that the army of young enthusiasts marches on undeterred. On the whole, these are not your average drug users. Nitrous oxide's harmless reputation is attracting large numbers of middle-class youths who otherwise would never dream of touching drugs.

Ruby Deevoy was one such teenager when she first encountered the gas. She has not touched it for two years, but at 23 she still has a vivid recollection of its effect on her. 'I first used it when I was about 16, at a festival,' she says. 'I made friends with the guys on the laughing gas stall and basically spent the whole weekend inhaling it.

'It didn't occur to me for a second that it might be illegal. They were selling it so openly.

'They showed festival-goers how to use it. You had to take it from a balloon, never direct from the dispenser, or you could freeze your lungs. I absolutely loved it and from then on I did it whenever I could.'

The initial effect, Ruby says, was one of unalloyed pleasure. That weekend at the festival, however, overindulgence led her to suffer severe hallucinations.

'At the beginning, everything kind of goes a bit clouded and all you can feel is the bassline of the music,' says Ruby. 'Then suddenly you burst out laughing and just keep on laughing. It is a really nice feeling, there's no denying that, but if I'd thought it was illegal I'd never have done it.

'I must admit I was hallucinating quite badly by the end of my first weekend taking laughing gas.

'On one occasion I crawled into a tent and thought there were dozens of people in there, but it was empty. Then I would blink — my eyes were closed for no longer than that — but in my mind I'd been in a coma.

'I also remember being mesmerised by the flaming torches on the site to the point where I very nearly walked face-first into them.'

Ruby, now a children's author living near Edinburgh, says she simply 'grew out' of the drug.

To this day, she remains uncertain about its legality, having been convinced it was a 'legal high'.

The reality, however, is that while she did not commit any offence in taking it, those who sold her the gas categorically did, as it's illegal to sell it for recreational purposes.

Those caught selling it without a licence can be jailed for up to two years. But few are convicted, due in part to the difficulty of proving the 'recreational purposes' aspect.

Nick Spears of the Medicines and Healthcare Products Regulatory Agency, says: 'The gas is commonly used on dental patients and for women in labour, but you don't go to the dentist every Friday night and you don't give birth every Saturday.

Old problem: As far back as the 18th century laughing gas was popular with the aristocracy. But so were opium and cocaine, pictured, and they have caused major issues in our society

'It carries serious long-term health risks for people who use it for fun.'

One of those risks is death. The International Centre For Drug Policy charts deaths in the UK from volatile substance misuse, including the gas.

Their most recent report, from 2010, notes that 'in 2008 there were two deaths (three in 2007) associated with the inhalation of nitrous oxide, which had been obtained for non-medical purposes'.

Finding more up-to-date figures is problematic, as the report is not currently active because of Department Of Health belt-tightening. But according to Stephen Ream, the indications are that the death toll has carried on in the same vein.

He adds: 'It's not just adults taking it. There is evidence that the users are getting younger, which is a real worry.'

Police as far afield as South London and Somerset have been alerted to children as young as 11 inhaling nitrous oxide.

Discarded canisters — used in the catering industry to pump whipped cream from dispensers — are routinely found in parks and playgrounds, and the drug is readily available on the internet. A pack of 24 canisters and a dispenser can be purchased for just £20.

Ruby Deevoy's mother Jacqui, a writer, was surprised to hear that the drug's sale was illegal. She said: 'I took the photos of Ruby inhaling laughing gas at that festival. At that point I had an idea it was some kind of helium and that people were buying it to make their voices squeaky. I couldn't see any harm in that.

'I told Ruby if she wanted to buy it, she could. It made her giggle for a bit, then the effect wore off. I thought at that point that the N2O must be like the gas and air I was given when I gave birth to Ruby.

'I loved that stuff — during the course of an eight-hour labour, I got through two canisters.'

Such is the ease of availability that it has even infiltrated middle-class living rooms.

Jacqui continues: 'I have two friends, both women my age, who use it on a regular basis for recreational purposes. One of them likes to do it just sitting at home, watching the TV. She says it relaxes her. Each to their own. It's probably healthier than downing a bottle of wine every evening — I know plenty of women my age who do that.'

And there is the rub: like our old foe alcohol, laughing gas is nothing new. As far back as the 18th century it was popular with the aristocracy.