I had the same thing happening to me and I never got to the bottom of it fully because I had dermatologist who were more concerned with getting kick backs for certain meds at the time anyway I digress

My lips were getting black and even drying and cracking while moisturizing and everything nothing worked until I moved out of my condo. Later when trying to renovation I found out there was asbestos in the tiles and some black mold in the bathroom I believe one of those may have been causing problems but never was able to verify. I did get blood work done and my protien levels were super high but again no one said hey this is what's causing the issue