Don't question Alicia Keys' choices, Adam Levine found out the hard way

Adam Levine found out the hard way when the three-time Grammy winner questioned the 15-time Grammy winner's choice of skin-wear on the set of US reality singing show, The Voice, where they both act as coaches.

The Maroon 5 frontman was asked by Howard Stern about Keys' au natural look and Levine couldn't help himself in revealing to the American shock jock that sometimes her no makeup look does actually involve some makeup.

"She was putting on a little bit of makeup," Levine told Stern, "and I was like, 'Oh, I thought Alicia doesn't wear makeup'."

"I do what the f--- I want," Keys replied.

This Girl is on Fire.

Aware of the mess he got himself into, Levine responded to Keys: "I love you so much."

The pianist and female activist decided to embrace the skin she is after years of fame and feeling insecure.

"Women are brainwashed into feeling like we have to be skinny, or sexy, or desirable, or perfect. One of the many things I was tired of was the constant judgment of women. The constant stereotyping through every medium that makes us feel like being a normal size is not normal, and heaven forbid if you're plus-size. Or the constant message that being sexy means being naked," she wrote in Lenny Letter last May.

"Every time I left the house, I would be worried if I didn't put on makeup: What if someone wanted a picture?? What if they POSTED it?

"These were the insecure, superficial, but honest thoughts I was thinking. And all of it, one way or another, was based too much on what other people thought of me.

"I don't want to cover up anymore. Not my face, not my mind, not my soul, not my thoughts, not my dreams, not my struggles, not my emotional growth. Nothing."

She made the choice to stop wearing a full face of make-up when she posed fresh faced for her album's artwork after being encouraged by the photographer, Paola Kudacki.

"I was shocked. Instantly, I became a bit nervous and slightly uncomfortable. My face was totally raw. I had on a sweatshirt! As far as I was concerned, this was my quick run-to-the-shoot-so-I-can-get-ready look, not the actual photo-shoot look. So I asked her, "Now?! Like right now? I want to be real, but this might be too real!!," she said.

For skin that glows like the top of the Chrysler Building, Keys gave up dairy, has regular facials and upped her water intake.

"It took me forever to get this skin," she told Elle UK "I mean, I know how it feels to have a face full of bumps and pimples. I lived through that in the public eye. But when I first got pregnant, I started to eliminate dairy from my diet and drank a lot more water, which made a huge difference to my skin."