Zayn Malik was banned from growing a beard or dying his hair when he was in One Direction.
The 23-year-old singer - who quit the group after over four years of chart success in March 2014 - admits he "rebelled" against the strict restrictions that were placed on himself and former bandmates Liam Payne, Louis Tomlinson, Harry Styles and Niall Horan over the way they looked.
He said: "There were certain restrictions in terms of the way that we could come outside of that young teen boy look.
"Mainly my beard, honestly. I wasn't allowed to keep it. Eventually, when I got older, I rebelled against it, and decided to keep it anyway. That was just because I looked older than the rest of them.
"That's one of the things that is now quite cool. I get to keep my beard. I also wanted to dye my hair when I was in the band, but I wasn't allowed to."
The 'Pillow Talk' hitmaker admitted the main reason why he left One Direction was his lack of "authenticity".
Asked if he struggled with his own authenticity while in the group, he told Complex magazine: "That was something that was always underlying, and ended up as the main factor of me leaving in the end. It was about denying the authenticity of who I was, and what I enjoyed about music, and why I got into it.
"That was always there. It was one of the things that wasn't going to go away, so I had to go away."
But Zayn insists his departure doesn't mean he is ungrateful for all the things he achieved in the band.
He added: "No one can ever say I was ungrateful, even though it sort of comes across that way when I mention that I was frustrated with the band. That's not the case at all. That was just an experience that had to be dealt with at the time. With the music that I'm doing now, I get to express myself, and that creative tension is gone."
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