"Guys, I'm actually scared right now," said a young teen in a YouTube video. "Oh my gosh that was so dumb of me."
That video and many others now circling the internet show a disturbing new challenge.
What he's doing is dumb and dangerous.
It's called the Ice and Salt challenge and it's landing many teens in the hospital.
"They put salt on their arm, they get an ice cube, they rest it on the salt and they see how long they can keep it on there," said Hillsborough County Fire Marshall Tammy Zurla.
What they don't know is they're creating a chemical reaction that sends temperatures plunging to around 5 degrees Fahrenheit.
"At first it will burn but then it gets so cold it mimics the same thing as frost bite," said Zurla.
Hillsborough County fire says it can lead to large welts and even permanent damage.
"Second and third degree burns, that's bad news, again lasting damage, nerve damage," said Zurla.
We went to USF's chemistry department where Dr. Jhon Figueroa showed us just how fast the temperature can change.
"This change in temperature can go very quickly, less than thirty seconds you can go from 0 Celsius to to minus 14," said Dr. Figueroa.
The temperature of the pile of ice we're using for the demonstration sits around 32 degrees Fahrenheit. Once the salt is added, those temperatures drop down more than 25 degrees in seconds.
"Don't try this at home, this is not kidding, this is not a game, you will get burned," said Dr. Figueroa.