Why Leona Lewis stopped straightening her hair

— -- Leona Lewis started straightening her thick, curly blond hair soon after signing her first record deal at age 20, but after going through a health scare a year and half ago, she decided to put down her flat iron and embrace her natural curls.

The 32-year-old singer, best known for her hit single "Bleeding Love," shared in a new essay on Glamour.com why she made the change after years of straightening her hair.

After winning Britain's "The X Factor" in 2006, Lewis entered the music industry at a time when images of straight hair were everywhere. "Gradually I started wearing my hair straight too, especially on photo shoots, where a lot of stylists didn’t know what to do with curly hair," she said.

Straight hair also made her feel more "polished," she admitted.

After straightening her hair for years, Lewis said she began experiencing symptoms of chronic fatigue, along with pains in her neck and throat, about a year and a half ago.

"It was a pretty hard time, and after a bunch of tests, I found out I had an autoimmune condition called Hashimoto’s disease, which affects mostly women," she wrote.

Hashimoto's leads to chronic thyroid damage, with symptoms similar to an underactive thyroid gland -- fatigue, weight gain, increased sensitivity to cold, depression and muscle aches.

"When my symptoms were the most severe, I could hear my body telling me that I needed to slow down. I also started to feel tired during performances. I began taking medication but also turned to Ayurveda (my mum is a master herbalist) to help heal my body naturally," Lewis wrote. "I just got to a point where I wanted to start over physically and emotionally. I started eating better and I stopped straightening my hair."

Lewis ended up shifting her entire beauty routine.

"Having an autoimmune disease really made me take a long, hard look at how I can reduce the toxins I come into contact with daily," she said. "I started using natural skin care and hair products (this inspired me to create a safe beauty brand for women, which I’m working on now), but I still had hesitations about wearing my hair curly at first."

The singer had to re-learn how to care for and style her curly locks.

"It was a rediscovery for me that curly hair is actually so versatile," said Lewis, who will sometimes scrape it back in a "super clean low bun."

Now she can't imagine going back to straight.

"If someone said, 'I want to blow-dry your hair straight now,' I would be like, 'No way!' I’d look like an alien," she said. "It just wouldn’t be me."