Some of the things I have seen in YT videos: a high titanium dioxide content in the PMU ink can give chalky lips over time. Titanium oxide pigment can not be removed from the lips*. Iron oxide pigments in the PMU ink can become absorbed by the body in people with anaemia, leaving behind the other remaining pigments in the ink. The lip shade then changes when the iron oxide is missing. (* I don't know yet how they fix this when it can't be removed. Presumably they have to tattoo over it somehow).
Some of the things I have seen in YT videos: a high titanium dioxide content in the PMU ink can give chalky lips over time. Titanium oxide pigment can not be removed from the lips*. Iron oxide pigments in the PMU ink can become absorbed by the body in people with anaemia, leaving behind the other remaining pigments in the ink. The lip shade then changes when the iron oxide is missing. (* I don't know yet how they fix this when it can't be removed. Presumably they have to tattoo over it somehow).