Daniel Radcliffe fell ill after accidentally ingesting chemicals on the set of his new movie Horns.
The Harry Potter star was filming in snowy Canada and was not aware a preparation had been added to pipework in his trailer to stop the water freezing.
Radcliffe consequently drank from the same source, and was off work for three days after falling sick.
He revealed the drama on U.S chat show Conan, saying, "It was all non-potable water that comes out of the tap... I didn't know that. So I drank a full cup of non-potable water so I guess like half anti-freeze or whatever it would have been.
"I got horrendously ill... It was a disgusting, feverish three days.
"Then a couple of weeks later I went to drink another glass of water in hair and make-up and they said, 'What are you doing? Don't do that... You can't drink that water'.
"I went back and checked my trailer and there weren't signs in it that said, 'Don't drink this water'."