With all the Instagram filters blurring out our skin and giving us so-called “flawless” faces, it’s refreshing when celebs get real about having less-than-perfect skin. On Monday, Hailey Bieber opened up about her perioral dermatitis and the triggers that cause her skin-condition to flare up. It’s a super-common condition but one that can be tough to treat because everyone has different triggers. It seems though, that Bieber knows her skin and why it happens in the first place.

According to the American Academy of Dermatology Association, perioral dermatitis is a rash that looks small and acne-like. Sometimes it burns, itches or even flakes and other times it feels like nothing much at all but a nuisance. Usually, perioral dermatitis pops up around the eyes, nose and—most commonly—mouth.

“This is day three so it’s calmed down a lot,” Bieber wrote on Instagram, circling a rash on her cheek. “Since I like to be as transparent as possible about my skin, I have something called perioral dermatitis, which I’ve known I’ve had for a few years now. It gets triggered by different things and usually shows up on my cheeks, around my mouth or sometimes around and under my eyes.”

She goes on to reveal some common triggers, including using a new “harsh” skincare product, weather, face masks and sometimes sunscreen.

Instagram.com/haileybieber.

In continued Instagram stories, she adds that laundry detergent is another big trigger, which is why she only uses hypoallergenic kinds (it’s most likely the dye or fragrance that’s triggering her). She also sticks to gentle skincare with anti-inflammatory ingredients that “won’t trigger a dermatitis breakout.”

Bieber finishes her story by warning fans that self-diagnosing is a “no, no.” She was only able to get a proper diagnosis to help her skin once she saw a dermatologist. Often, you need a prescription cream if at-home treatments don’t work after a few weeks.