A "vulnerable and deeply troubled" woman with bulimia died after taking "slimming pills" containing chemicals used in First World War explosives, a court has heard.
Eloise Parry, 21, took Dinitrophenol (DNP) capsules, the side effects of which include multiple organ failure, coma, and cardiac arrest.
She died a "most distressing death", the court heard.
Bernard Rebelo, 32, from Gosport in Hampshire, is standing trial for her manslaughter.
He is accused of buying the yellow powder from a chemical factory in China and selling it on as tablets to people around the world - including Ms Parry.
DNP is described online as "straight poison" and "the devil's cut agent" and was used as a base material for munitions in the First World War.
Internet forums compare its consumption to "Russian roulette", Prosecutor Richard Barraclough QC said, adding: "If you take it, you might live, or you might die."
Ms Parry, from Shrewsbury, started taking DNP in February 2015 and died two months later, the Old Bailey was told.
She was described as having a "morbid dread of fatness" and "simply unable to control herself when it came to [DNP] consumption".
The chemical is particularly dangerous for people with eating disorders because the level of toxicity is relevant to a person's weight.
Ms Parry was admitted to Wrexham hospital after collapsing in March 2015.
She texted a friend, saying: "I f***** up. A and E. DNP overdose. Feel so f****** stupid. I knew I could not control my eating disorder well enough to take them safely, I knew it."
She added: "It's not going to matter how skinny I am if I'm dead."
She messaged again three days later, writing: "I don't want to die, I never meant to hurt myself, I just felt so desperate.
"I've been trying so hard to be okay with my body and myself that I pushed down all of those negative feelings instead of dealing with them."
The prosecution alleges that Rebelo bought DNP from a chemical factory in China and sold it on two websites, both of which have since been taken down.
He ran his business from a flat in Harrow in northwest London, the court was told.
Prosecutors argue that he knew the dangers of what he was selling.
In 2013, an associate who had taken DNP texted Rebelo to say "I feel like s***, I'm too hot" and "I'm drinking s***-loads of liquids".
Mr Barraclough told the court: "He knew it was dangerous, not only because one of his associates had consumed DNP and had suffered some of its toxic effects... but because it was well-known that any number of authorities and organisations were warning against the dangers of consuming the chemical."
Rebelo denies manslaughter and the trial continues.