"Where it really impacted me was how self-conscious I became about it," Kendall wrote. "It completely ruined my self-esteem. I wouldn't even look at people when I talked to them. I felt like such an outcast; when I spoke, it was with my hand covering my face."
The Keeping Up With the Kardashians star says she was dependent on her family more than ever during this time as her older sisters, Kim, Kourtney and Khloe Kardashian, also struggled with acne when they were growing up.
"I was thankful we always talked about it in my family," Kendall added. "They would help me work on my feelings about it and how I would move past that stage of my life. I remember on Christmas Eve one year, I was sitting in my bedroom upstairs crying and Kim walked in and we talked about it together -- she felt so bad for me."
Kendall has been acne-free for three years after seeing a dermatologist and beginning Laser Genesis treatments, a procedure that helps to eliminate wrinkles, large pores and diffuse redness and scars. "Slowly, I'm working towards not caring and I'm just in so much of a better place about it all now that I'm older," she said. "I realized that it's a part of life for some people and it doesn't define who you are."
When Kendall spoke with ET, she revealed the best beauty tip she ever received from her sisters. "Sunscreen. They always told me to wear sunscreen," she dished dished. That's not the only trick the Kardashians have up their sleeves. Check out our interview: