Biomedical aspects of tattooing have been extensively discussed in literature, however pathophysiological effects of tattoo inks in the human body are still unexplored. Oxidative stress is considered responsible for the adverse effects of tattooing, however no experimental evidence for tattoo ink-related oxidative stress in the human body currently exists. The aim was to examine the effect of a blue tattoo on skin redox regulatory network (RRN) parameters in a single human subject. Skin surface oxidation-reduction potential (ORP) was analyzed with a PH60F flat probe. Interstitial and intracellular fluid enriched capillary blood from the tattoo and the control area was extracted and analyzed with I2/KI-stabilized microORP, nitrocellulose redox permanganometry (NRP), carbonato-cobaltate (III) formation-derived H2O2 dissociation rate assay, 1,2,3-trihydroxybenzene autoxidation assay, thiobarbituric reactive substances (TBARS) assay and 5,5,'-dithio-bis-(2-nitrobenzoic acid) (DTNB)-based determination of free thiol content in low molecular weight and protein precipitate fractions. Surface ORP analysis revealed a greater antioxidant capacity of tattooed skin in comparison with the control (CTR). Capillary blood analysis confirmed greater reductive capacity in the tattoo sample both by microORP (-4.33 mV vs CTR) and NRP (+10.8%). Hydrogen peroxide dissociation rate (+11.8%), and protein sulfhydryl content (+8.5%) were increased, and lipid peroxidation (-15%) was reduced in the tattoo sample in comparison with the CTR. In this N-of-1 study, RRN of tattooed skin was shifted toward a more reductive state with all parameters indicating reduced levels of oxidative stress in comparison with nontattooed skin. The local antioxidant effect of copper(II) phthalocyanine provides one possible explanation of the observed effects.