Twitter finally pulled two controversial advertisements after users complained they were triggering epilepsy episodes.

Rachel Bremer, international director of communications at Twitter, acknowledged the issue in a tweet to the charity Epilepsy Action.

The original ads were posted via Vine, Twitter's looping video platform, to promote Twitter's #DiscoverMusic campaign, which is trying to attract more artists to the social network. The two Vines had six seconds of flashing video, which was enough to trigger epilepsy. 

Epilepsy, also known as seizure disorder, is where nerve cell activity can be disturbed by bold patterns or flashing lights, which causes seizures. According to the Mayo Clinic, about one in 26 people in the US will develop a seizure disorder.

Twitter's advertisements were up for 18 hours before they were finally removed early Friday morning.

"Eighty seven people are diagnosed with epilepsy every day and that first seizure can often come out of nowhere," Epilepsy Action's deputy CEO Simon Wigglesworth told BBC. "For a huge corporation like Twitter to take that risk was irresponsible."