By Finlo Rohrer
BBC News Magazine
"My body felt like it was a palette of paint thrown on a canvas and slowly moving down it."
This description of the effects of digesting the plant salvia divinorum - a relative of common sage - sounds like a parody of 1960s mind-expanding hippies. But it is not untypical of a curious YouTube-centred subculture.
Mexican shamans have been using the plant as part of religious rite for thousands of years, but it is now one of a range of "legal highs" sold on both sides of the Atlantic.
Smoked, the effect can be intense but lasts as little as 10 minutes, while chewing it creates a longer period under the influence. Its defenders say it is neither toxic or addictive, but legislators have been concerned enough for it to be banned in Australia, a number of European nations and a handful of US states.
Users can experience uncontrolled laughter, a temporary inability to speak, dramatic visual and auditory hallucinations, uncoordinated movement, a feeling of being out of the body and a wide range of other unsettling phenomena.
In the US, following the suicide of a teenager last year who had at some point smoked the plant, there were calls for a federal ban.
Here, Labour MP for Bassetlaw, John Mann, recently tabled an early-day motion demanding the government urgently rectify its "oversight". "Some claims made about salvia are very bad. People will be shocked by this," he said.
Botanist Daniel Siebert is regarded by some as the guru of salvia, and since 1991 he has been examining the chemistry and history of the substance, as well as using it and selling it. He fears that its widespread availability and irresponsible use by teenagers may lead the US authorities to ban it.
"A lot of people would say even if you don't have any evidence of psychological harm, just the fact it causes intense hallucinations is dangerous in itself. That can be a dangerous thing to do. You could jump out of a window. In that sense you could make an argument that there is a legitimate concern."
Mr Siebert says salvia should be used in a safe environment, supervised by someone sober, and in low doses. The consequences of ignoring this advice can be unfortunate.
"One person put his arm through a window because he didn't see a window. Another person while he was immersed in this intense visionary state when he regained his senses found some of the furniture in the room was smashed up and he had a broken shoulder. He was running around not knowing what he was doing."
Mr Siebert says his first experience, chewing raw leaf, was pleasant.
"I noticed some shifts in visual perception, objects had a glow or coloured aura. I looked up at the hills. There were Hobbit-like houses nestled into the hillside. There was light coming from the windows. There was something fairytale-like about the scene, there was something very comforting about the whole thing."
Others, particularly those that smoke a stronger extract, often have a bad time of it, experience a much more dramatic "visionary" effect that leaves many unnerved.
"They find it frightening or disorientating, not a good substance for a social situation. Most people find it uncomfortable," Mr Siebert suggests.
And this perhaps goes to the root of the fear of salvia. While studies have suggested depressive effects in rats, there is yet to be a major scientific study completed into its effects on humans. But there is perhaps understandable fear over the legality of such a powerful hallucinogen.
Tim Kendall, deputy director of the research unit of the Royal College of Psychiatrists and a consultant psychiatrist, says there are grounds for concern and that "all hallucinogens should be treated with caution", but usage is clearly rare in the UK. He has never seen a patient with problems where salvia has been mentioned.
Clinical pharmacologist and addiction expert Professor Fabrizio Schifano, of the University of Hertfordshire, agrees the hallucinogenic nature of salvia is enough for it to be of concern.
"Do I have a reason to be concerned? Yes. Do we need further studies? Yes."
One thing that concerns him is the theory that interaction with the receptors in the brain that salvia acts on may be linked to schizophrenia. Salvia's role in brain chemistry therefore needs more research, Mr Schifano says.
But even if one cannot conclusively establish that a substance like salvia is toxic or harmful to mental health, can't one take the view that powerful hallucinogens are necessarily something bad for society and ban them anyway?
Access to pleasure
Bioethicist Professor Julian Savulescu, a former doctor and director of the Oxford Uehiro Centre for Practical Ethics, says one should be able to argue at least for "direct pharmacological effects or disturbance in social function" before considering restricting individual freedoms.
"There has been a long history of attempt to control access to pleasure.
"I can't see a good reason to interfere in individual liberties when people aren't harming themselves or other people. If they were inducing altered states through meditation or chanting, people wouldn't think of asking for a ban."
It is a view that the UK government is yet to contradict. The Home Office says: "We are not aware of any evidence of significant misuse of this plant and we have no plans to review its legal status."
In practice though, it may be the strange qualities of the plant that stop it spreading beyond the current YouTube minicraze.
Steve Henderson, whose firm sells herbal products advertised as "not for human consumption", has been stocking salvia for five years. He has taken it. Once.
"Personally, I think it's awful. It was very intense, quite hard to understand what exactly was going on. It's something that I've never repeated. People will try it and not go back."