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Aerosol canisters of nitrous oxide are readily available for sale online in Britain, marketed as whipping agent for desserts and cream, for as little as £10 for a box of 20. And high profile stars like footballer Raheem Sterling and actress Michelle Keegan have been caught indulging in the trend.

But ophthalmologist and laser eye surgeon David Allamby, clinical director of London's Focus Clinic, says nitrous oxide can lead to irreversible damage to a person's eyes. Nitrous oxide abuse can induce vitamin B12 deficiency, which in turn can lead to depression, hair loss and blindness, he said.

He added: 'The links between vitamin B12 deficiency and Hippy Crack are well established, following a series of research papers.'And this B12 deficiency causes damage to the optic nerve, something known as optic neuropathy.

It could be helped by huge supplement injections of B12, but the vision loss could be irreversible, especially if advanced. And chronic abuse of nitrous oxide gas could not only lead to blindness, but a host of other problems, too, including nerve damage. I'd argue that if more and more people in the UK continue to abuse this so-called legal high we could be facing a sight loss epidemic in the months and years to come.'

The warning comes just days after 18-year-old Ally Calvert, from London, was found collapsed in the street having apparently 'ingested nitrous oxide'. He later died in hospital.

Nitrous oxide itself - which is a chemical compound with the formula N2O - is used by some dentists as an anaesthetic. While it's not illegal to possess and inhale the substance, it is against the law to supply it to anyone under the age of 18.

The Medicines and Healthcare Products Regulatory Agency said: 'Any retailers selling or supplying an unlicensed medicine containing nitrous oxide for inhalation purposes, or allowing it to be supplied other than in accordance with a prescription, are in breach of UK medicines regulatory requirements.'

The links between vitamin B12 deficiency and Hippy Crack are well established, following a series of research papers. And this B12 deficiency causes damage to the optic nerve, something known as optic neuropathy

Ophthalmologist and laser eye surgeon David Allamby

Last year, the Local Government Association (LGA) issued a health warning and said that councils were seizing large hauls of the drug using by-laws and street trading legislation to take action. But Martyn Hooper, chairman of the Pernicious Anaemia Society, has urged the UK government to do more to stamp-out nitrous oxide usage. Writing in his upcoming book, What You Need To Know About Pernicious Anaemia and B12 Deficiency, he states that nitrous oxide is now the 'second most used recreational drug after cannabis', according to Home Office figures.

He added: 'It has more users than cocaine. Nitrous oxide causes the user to laugh - hence its more common name "laughing gas" and it has one lasting side effect - it "inactivates" vitamin B12. So the message is, even if you are tempted to join the party and sniff a lungful of N2O be aware of the implications of B12 deficiency. A quick search of YouTube shows many videos of young people sucking in balloons of nitrous oxide and having a great laugh. Be careful.'

In September 2013, England defender Kyle Walker issued a public apology after he'd been caught inhaling nitrous oxide.

He said: 'I have now been made aware of the health risks associated with the practice and accept that my actions were of poor judgement. I hope this will in no way influence or encourage others into putting their own health at risk.'