The country star, 26, was diagnosed with the chronic autoimmune disease at age 2. By age 6 she was covered in red, scaly patches that would crack and bleed. "Not only does that take a physical toll on your body, but it takes an emotional toll," Rimes tells PEOPLE. "I was very self-conscious."

The struggle was made even harder as a young woman in the public eye. "It's amazing to me how many people say, 'Oh my God, I would never ever have known,'" says Rimes. "I was hiding it for so long."

Symptom-free for five years thanks to medication, diet and stress management, Rimes is sharing her experience on behalf of the Stop Hiding campaign in a new PSA to raise awareness of the disease, which affects as many as seven million Americans.