Gwen Stefani has been in the music business for over two decades, so it makes sense that she would have had a little work done, right?

Doctors think the 47-year-old has gotten plastic surgery, though the mother-of-three has never admitted to going under the knife before. But one thing seems certain among specialists: the singer is a fan of injections.

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"Gwen appears to have done Botox," Michael Salzhauer, aka "Dr. Miami" — who hasn't treated the blonde beauty — told Radar Online in a 2016 interview. "But she's also had her already luscious lips plumped up to perfection. Aside from that, she's just most likely had a series of chemical peels. She looks great."

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Gwen in 2000 (left) vs. 2017.

Beverly Hills plastic surgeon Dr. Sheila Nazarian, who hasn't worked with The Voice coach either, agreed with Salzhauer's assessment, telling the site, "Gwen looks like she has had a lot of fillers in her face, Botox, and chemical peels."

"She's most likely also had some laser treatments and, if she is into the trend that all of Hollywood is doing right now, she has most likely tried platelet rich plasma, commonly called the Vampire facial," Nazarian added.

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But cosmetic specialist Zara Harutyunyan thinks it's more than just Botox. "It looks to me like Gwen also has undergone Ultratherapy, which is a non-surgical face lift and neck lift," she shared.

Scroll through the gallery below to see how the Grammy winner has changed over the years!