Amanda Seyfried Gives an Update on ‘Mamma Mia’ 3 (Exclusive)

Amanda Seyfried is a super trouper when it comes to her eczema.

However, the Mamma Mia star explained that she has been dealing with perioral dermatitis since she was 19.

"You might be thinking, 'What's that on her face?'" Amanda, 39, said in a March 18 video for Vogue's Beauty Secrets series. "That's my eczema."

She continued, "When I was 19, I started developing the rash, and I learned about a lot of medicated products. I learned a lot about just products in general from my dermatologist at the time.”

Amanda has since tried multiple techniques to improve the condition, which can be caused by one's immune system, genetics or environmental or emotional triggers, according to the Cleveland Clinic.

"It's funny how eczema makes you feel," she explained. "Two years ago, I had another flare up and I cut out dairy. Boy, it was hard. Bye-bye cappuccinos, black coffee all the way."

However, the actress thinks her lifestyle and healthy habits after having children—Nina, 7, and Thomas, 4, who she shares with husband Thomas Sadoski—have helped her skin to clear up.