The substance is used by fitness fanatics to boost their stamina and increase energy levels.
But young partygoers are inhaling or swallowing it to get high. One lad died after swallowing two teaspoons of the powder – equivalent to almost 70 cans of energy drink.
Many firms which sold so-called legal highs such as Spice and Black Mamba went out of business when they were banned last year.
But some began selling the pure caffeine powder instead.
Unscrupulous sellers even market it in “snorting kits” resembling the drugs paraphernalia used by cocaine addicts.
The powder is legal but has been linked to a string of deaths in the UK, Europe and the US. Even relatively small amounts of it can trigger a heart attack.
Tubs of the powder and tablets are freely available on sites like eBay and Amazon and also on the high street.
Reputable sellers in the sports world offer tips on dosage and information about the potential health risks.
But other sellers are marketing the powders as the latest “legal high”, even aiming them at children by offering them in small packets at pocket money prices.
One trader offers 0.5g sachets with a smiley face logo for £4. A 1g packet Snowblow Blowout at £7 is described as “caffeine power party snuff”.
In his advert the seller says that it packs a “punch”.
Another trader is offering three packs of pure caffeine powder plus a snorting kit consisting of a small mirror, razor blade, glass bottle and wallet for £15.99.
The advert boasts: “You’ve seen all our new powders exempt from the ban and think they’re great alternatives? Well, look no further than our exciting pick me up energy snuff pack!
“We’ve put together our best caffeine-based powders in this brilliant snuff pack featuring 2.5g of the good stuff to liven your senses. A sociable kit with only ups, no downs.
“We’ve done our fair share of testing – it’s a hard job but someone’s got to do it – and the perks will get you feeling great and energised in no time.
“Ideal when compared to the old research chemicals as you can stay up till 3am and still be able to face the day.
“We won’t hear of any wrecked plans with these beauties. So, get trying and let us know what you think.”
Neither seller warned about the risks of an overdose. In 2010, a partygoer died after swallowing two spoonfuls of pure caffeine he had bought on the internet.
Michael Bedford, 23, from Mansfield, Notts, washed the substance down with an energy drink.
The combination left him with a massive 251mg of caffeine per litre of blood in his system.
An inquest heard the dose was the same as 70 cans of Red Bull drink.