Warning over 'thumb blowing pass out' teen TikTok challenge

Aussie parents are being warned about a dangerous new TikTok trend that's seeing teens make themselves pass out to experience a brief 'high'.

Videos of teens trying the "thumb blowing pass out" challenge have spread worldwide, with some leading to dangerous ends, including seizures, head injuries and trips to the hospital.

In one case, a 12-year-old boy from the UK was put into a coma for 36 hours after he fell and hit his head while doing the challenge.

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The trend sees teens standing leaning over their knees breathing deeply before standing up suddenly and blowing out of their mouth with their thumb in their mouth.

Now, the trend is spreading among local teens, with one Sydney mum sharing details of an incident last week involving a 13-year-old boy.

The boy was out with friends when he undertook the 'challenge' and hit his head against a metal post as he fell.

"His parents took him to hospital as they were worried he had a concussion, but thankfully that was ruled out," she said.

"He ended up with a bump on his head and two black eyes, but it could have been much worse."

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The dangerous challenge is not the first to emerge on TikTok. Last year, the TikTok "Blackout" challenge saw teens around the world trying to choke themselves while holding their breath to make themselves pass out.

A 12-year-old boy from the United States was left "brain dead" after he attempted to choke himself with a shoelace for the trend.

Another 10-year-old girl from Italy died from the challenge.

Doctors have since urgently warned children not to partake in the challenge, and parents to be wary of what content their children might be following online.