Yeah, it happens. As frustrating as this is for your client (and you!) there’s nothing usual here.
Stress and hormones, seasonal changes, using new products they didn’t tell you about, slacking off on home care and salon appointments; all can lead to a sudden return of acne lesions.
But don’t panic. What was once under control can normally be controlled again through investigating whatever influences might be involved, and skincare practices that need to be revived or altered.
So long as someone is subject to an acne condition so will they possibly experience on and off periods of breakouts, skin eruptions, and relief.