For Kim, it's her psoriasis (an autoimmune skin condition).
Kim has been very vocal about her struggles with it in the past, which she has been battling since 2011, but over the weekend, she took a tabloid on after it made fun of her "bad skin".
"Makeup mogul suffers bad skin day in LA ahead of Master Class beauty seminar," it read.
"It’s psoriasis all over my face. ," Kim replied.
The symptoms of a psoriasis flare-up can include red and flaky (sometimes itchy), patchy skin.
Psoriasis is one of the most common autoimmune diseases in the world, as it affects 7.5 million people in the United States alone! So, it's nice that someone like Kim who has such a large platform, is constantly open about her struggles.
Just another reason why we love her!