The 22-month-old girl had been crawling on the path alongside her parents on Monday morning when she found and licked the paper.
Soon after, her pupils dilated and her parents noticed a change in behaviour.
She was rushed by emergency helicopter to Amstetten hospital where doctors realised she probably have licked a discarded drug packet, that may have been carrying LSD or cocaine.
The baby was then transported to Linz hospital where she is in a stable condition in intensive care.
It was initially suspected that the foil might have been discarded by people attending the annual “Beachparty” that took place on Saturday evening near where the incident happened.
Organiser of the event Gabriel Kritzl said, however, that the foil could not have come from their event.
“Our festival area was blocked off by high fences on Monday morning and we only began taking it down early this [Tuesday] morning,” he said. “If it had been to do with us, we would have noticed the incident because we were constantly there.”
He added that the grounds around the festival were so muddy it would have been difficult to go for a walk there.
Kritzl said it may have been from another group holding a party nearby.
“Some 100 metres downstream some people who looked like hippies were apparently having a private celebration or some kind of event,” he said.