They said pure caffeine powder posed a serious risk of overdose and poisoning.
These essentially 100% caffeine products could deliver caffeine levels equivalent to 28 cups of coffee in a single teaspoon.
In its warning NFA toxicologist Emma Halldin Ankarberg said the authority had found one product advising consumers not to exceed doses of 200 milligrams – or one-sixteenth of a teaspoon.
The caffeine content of a single can of Red Bull is 80 mg/250 ml, while an average cup of coffee contains around 95 mg.
Last year the European Food Safety Authority (EFSA) said in a risk assessment up to 400 mg of caffeine a day and 200 mg in a single session ﴾two hours﴿ did not pose a health risk for general population adults.
Yet she said this was impossible to measure out accurately without access to special analytical equipment and given the concentration a slight error could have huge implications.
Last year the US Food and Drug Administration (FDA) also warned against pure powdered caffeine sold in bulk bags over the internet.
“The FDA is aware of at least two deaths of young men who used these products,” it said at the time.
It also issued warning letters to five distributors of pure powdered caffeine and promised to "aggressively monitor" the market for these products and take appropriate action, which could mean product seizure or an injunction.
Like Sweden’s NFA, it said it was near impossible to accurately measure pure powdered caffeine with common kitchen measuring tools and it was therefore easy to consume a lethal amount.
“Pure caffeine is a powerful stimulant and very small amounts may cause accidental overdose. Parents should be aware that these products may be attractive to young people.”
Sweden’s poison centre warned amounts in excess of 600 milligrams could cause unpleasant symptoms and require hospitalisation.
Symptoms of poisoning - like nausea, vomiting and tremors and at higher doses persistent vomiting, seizures and heart rhythm disturbances - usually occurred within an hour of ingestion but could also happen within ten minutes.