A new phone app that lets users ask anonymous questions over Snapchat has raised concerns over online bullying.

Snapchat add-on YOLO, an acronym for “You Only Live Once,” allows users to anonymously send messages and questions.

At least one expert is concerned the app could be a portal for bullying.

“My primary concern is that we know anonymity and aggression go hand-in-hand,” Professor Tracy Vaillancourt from the University of Ottawa’s department of education said.

“The fact that it has an anonymous platform means that it’s going to be used by people with sinister intent.”

YOLO, which is aimed at teens, was the most-downloaded iPhone app in the U.S. and U.K. just a week after its release, according to the BBC.

Professor Vaillancourt believes it causes harm to the most vulnerable in society, after a number of reports of harassment on the platform.

“I think we need to do a better job at monitoring social media and holding people accountable and we haven’t figured that out yet,” she told CTV News Channel.

“People who monitor these programs will take down vicious comments and the like, but a lot of times they stay up.”

The app is made by French start-up company Popshow Inc.

U.S. child safety group Protect Young Eyes has branded the app’s 12+ rating as too low. 

“Anonymity has always created a breeding ground for hate and very poor teen decision making,” a review on the site said.

“Do you know many 12-year-olds who consistently make great decisions over the long haul without accountability?”

The website suggested parents wait until their child is 16 before they use the app.