Hailey Bieber is "very diligent" about cleaning her make-up brushes since the dirt sets off her perioral dermatitis.

The 24-year-old model - who is married to pop star Justin Bieber - has become very "conscious" about the products she uses and revealed she can suffer flare-ups when she has her glam done constantly by make-up artists for work.

Asked if she is careful about what she uses on her skin, Hailey said: "Yeah, I definitely am. I'm conscious now in general. It's because I've gone through enough flare-ups of it where I've realised what might set it off or what's starting to irritate me that might bring it out.

The products I use are a big part of that. When I'm working, working, working, working, working a lot, my face is just getting touched a lot, and [people are using] different types of make-up with different ingredients; it can start to really irritate my skin, and I can start to see that it might cause a flare-up. If people use dirty brushes or anything by accident, that's another big thing. Or if I don't wash my own make-up brushes, which I'm very diligent about now. I think I've paid attention to — and I still pay attention to — what could irritate my skin."

When her skin does break out in a rash, the blonde beauty has a special medicine she has been prescribed by a dermatologist to help clear it up.

She added to POPSUGAR: "At a certain point, if you have a skin concern like perioral dermatitis, I do think it's important to talk to a dermatologist about what the best thing is to use for that, because I do think that in certain cases, a prescription medicine is going to be your best bet. That's why they exist, that's why dermatologists are there. I have something from a dermatologist I would use if I was having a really bad flare-up of perioral dermatitis."