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And so, to play such a diverse array of characters, Knightley would often dye her hair to whatever color was required for the role. But in doing so, the 31-year-old actress revealed to InStyle UK that her hair started falling out.
"I have dyed my hair virtually every color imaginable for different films. It got so bad that my hair literally began to fall out of my head," Knightley said.
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The Oscar nominated actress revealed that, instead of continuing to damage her hair, she's been using wigs for the past five years for her roles - which she said is the "greatest thing that's ever happened" to her hair.
Since then, Knightley's natural hair has been recovering. Yet, since giving birth to her first daughter, Edie, one year ago, she's found that her hair's actually become thicker than ever.
"I have naturally crazy, curly hair, and since I've had the baby it's become 10 times thicker. So now I've been finding quite a lot of dreadlocks," Knightley said.
Read more about Knightley's beauty secrets here.