In an interview with InStyle, Keira Knightley opened up about the serious toll that constantly changing her hair color for movie roles took on her locks. The regular dyeing was so damaging that her hair began to fall out.

"I have dyed my hair virtually every color imaginable for different films," she said. "It got so bad that my hair literally began to fall out of my head."

"So for the past five years I've used wigs, which is the greatest thing that's ever happened to my hair."

However, after becoming pregnant with her daughter, Edie, Knightley noticed that her hair began to grow back.

Her limp strands returned to their former glory, and now her hair is thicker and fuller than it ever has been.

While Knightley has been lucky enough to recover her strands, hair thinning is a common issue that many women suffer from. It can be triggered by a number of causes—stress, hormones, hair dye, over-styling, depression, and diet among them.

COURTESY: Harpers Bazaar