On April 11, 2016, it was announced as the fourth single off of their album.  It was released on April 15, 2016.
Music Times writer Carolyn Menyes stated: "Featuring handclaps and a repeating line of 'Switch it up,' Little Mix take on the freshly single hairdo in 'Hair,' and right off the bat it's clear that this song is going to be a post-breakup anthem for the ages. "I call my girl cause I got a problem / Only a curl is gonna solve it," the group sings in the opening lines. It's a theme that continues throughout the rest of the song. Against an intense drum beat and blasts of horns, Little Mix are sassy and confident about their new style with lines such as,' Cause he was just a dick and I knew it / Got me going mad sitting this chair / Like I don't care / Gotta get him out my hair.' 'Hair' is a fun girl power anthem, which is an art that Little Mix has mastered. And, let's be real, a song about this topic is long overdue." 
The album version charted at #35 on the UK Singles Chart when released as a promotional single. The remixed version charted at #11 on the UK Singles Chart. After the release of the remix version, the original reached a peak of #31 on the Singles Chart.
The music video was released on April 20, 2016. It was directed by Director X who also directed the Black Magic music video. The video starts with Leigh-Anne scrolling through Instagram until eventually seeing her boyfriend (Sean Paul) with another girl. Heartbroken, she phones the girls (Perrie, Jade and Jesy, as they come over to Leigh's house to cheer her up. The girls have a sleepover, dancing together, having pizza and getting ready in front of a mirror. Leigh's boyfriend calls her up, trying to convince her that he still loves her but her friends show her that he is not worth it. Leigh agrees and they continue having fun together.