Doctors say 16 year-old's kidney infection caused by drinking three cups of green tea every day for three months in a bid to lose weight.
The girl ordered two boxes of 100 teabags online, and most of the ingredients were written in Chinese.
It is the drink of choice for the health-conscious, but doctors have warned of the hidden dangers of green tea after a teenage girl who drank three cups a day for three months contracted acute hepatitis.
The 16-year-old complained to her GP of dizziness, nausea, stomach and joint pains. The doctor initially thought she had a urinary tract infection and she was sent home with antibiotics.
Two days later her symptoms had worsened and she went to the A&E department of Birmingham University Hospital.
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By this point, she was suffering from jaundice, causing her skin and the whites of her eyes to turn yellow, according to doctors who described the case in the journal BMJ Case Reports.
Her condition was deemed so serious that she was referred to the acute medical team, who believed she was suffering from hepatitis, a swelling or inflammation of the liver.
It can be caused by a virus, or when the liver is exposed to harmful substances such as alcohol.
The girl, who is originally from Yemen but was not named in the report, said she had not recently consumed alcohol or drugs, including over-the-counter prescription drugs such as paracetamol, nor had she travelled abroad.
Tea time: a tisaniere - glass teapo
But she recalled she had ordered two boxes of Chinese green tea online, and drank three cups a day for three months.
“I had bought the green tea over the internet to lose weight,” the teenager said.
“Most of the ingredients of the tea I bought were written in Chinese.
"I had only lost a couple of pounds but then started having horrible pains in my joints, and felt very dizzy and sick.”
The authors of the report said infections developing as a result of excessive herbal tea drinking were a “rare but recurring theme”.
Green tea, which is rich in a depression-fighting animo acid called theanine,has previously been lauded for its health benefits.
It has been suggested that its antioxidants help with breast, lung and stomach cancers. It has also been claimed that a cup can protect against dementia and Alzheimer’s and improve cholesterol levels.
But doctors identified green tea as the “causative agent” of the girl’s hepatitis, and ordered her to stop drinking it immediately.
“After ceasing green tea consumption, there was a rapid and sustained recovery of her hepatitis,” the report’s authors wrote.
They said it was possible that the addition of chemicals to the tea, perhaps to aid weight loss, or the use of pesticides on tea trees had contaminated the infusion.
“There is potential for pesticide-induced hepatitis to exist, especially from less regulated products ordered from developing countries over the internet,” said the report.
But the authors added: “We acknowledge that green tea is predominantly a very safe and healthy drink, with antioxidant properties.