The persistence of traditional tattoo inks presents an advantage for continuous and
long-term health monitoring in point of care devices. The replacement of tattoo pigments with
optical biosensors aims a promising alternative for monitoring blood biomarkers. Tattoo inks
functionalization enables the control of interstitial biomarkers with correlated concentrations in
plasma, to diagnose diseases, evaluate progression, and prevent complications associated with
physio pathological disorders or medication mismatches. The specific biomarkers in interstitial
fluid provide a new source of information, especially for skin diseases. The study of tattoo inks
displays insufficient regulation in their composition, a lack of reports of the related
complications and a need for further studies on their degradation kinetics. This review focuses
on tattoo optical biosensors for monitoring dermal interstitial biomarkers and discusses they
clinical advantages and main challenges for in vivo implantation. Tattoo functionalization
provides a minimally invasive, reversible, biocompatible, real-time sensing with long-term
permanence and multiplexing capabilities for the control, diagnosis, and prevention of illness;
it enables self-controlling management by the patient, but also the possibility of sending the
records to the doctor.