Niall Horan totally worried fans after he left in the middle of One Direction's performance of "18" at the Apple Music Festival. Basically, one minute he's on stage, and the next minute he's not! Fans even reported that an ambulance was sent to the venue to make sure that he was okay.

While he didn't go into specifics about what was bothering him while he was onstage, Nialler said that the heat was getting to him, so he may have just been dehydrated.

He later clarified that there was no ambulance and that he just got overheated.

Thankfully, he was feeling fine later that night, and even went out partying with Little Mix. It's good to see him recover so quickly! We're glad that he knows how to take care of himself and leave the stage when he needs to.

What do you think happened to Niall? Are you glad he's okay? Let us know in the comments!

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