Katherine Heigl has a makeup secret she’ll confess – she loves using beauty products.

“When I was in Rhode Island filming this summer, I went to Sephora for the first time,” she tells InStyle for its October issue. “It was like my holy mecca.”

The obsession has led to a transformation in her bathroom, which she says she’s reorganized to accommodate her products – some of which she gets for free. “I love getting those boxes,” she says.

And while the Grey’s Anatomy Emmy winner, 28, admits that her arms are wide open to freebies, she does have her limits. “There comes a point of gluttony that I can’t accept,” she says. “When that happens, I feel like I have to clean out and give stuff to my sister, mom and friends.”

Heigl says the obsession stems from being conscious of her looks to the point that she always wears full makeup in public: “I do not want to be the ‘Look What This Celebrity Looks Like Without Makeup’ picture.” And then she has what she considers her less-than-perfect attributes: her complexion and teeth.

“My skin is sensitive, so everything bothers it,” she says. “And I’m the jerk who keeps switching products and making it worse.”

Heigl wears an Invisalign retainer, which she removes in the interview before eating. “I got them because of this wonky tooth,” she says. “It’s awesome because every two weeks you switch to a new retainer. Pretty much the perfect way to describe Invisalign is Netflix for your teeth.”

For her InStyleHollywood Hair Makeover shoot, the self-professed product fanatic got to try on three different looks for three different covers. Posing with a glamorous updo, a short, brunette wig and her hair in loose ringlets, Heigl raved about the experience.

“To have these professionals turning you into someone else is pretty neat,” she says of the transformation – especially when it came to her hair. “I’ve always wanted to be a brunette because in a town of blondes, it makes me look a little more exotic,” she says.

Still, she has a favorite look of the three: “The Ingenue,” which she describes as “sexy but not overtly so.” The image – with her hair down and loose – seems to sum up Heigl’s style perspective. Says the actress: “I like simple hair and makeup.”

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