Background: Persons with cosmetic tattoos occasionally experience severe pain and burning sensation on magnetic resonance imaging (MRI). Objective: To explore the culprit magnetic substances in commonly used permanent makeup inks. Material and methods: 20 inks used for cosmetic tattooing of eyebrows, eyeliners, and lips were selected. Ink bottles were tested for magnetic behavior with a neodymium magnet. Eight iron oxide inks qualified for the final study. Metals were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The magnetic fraction of inks was isolated and analyzed by X-ray fluorescence (XRF). Magnetic iron compounds were characterized by Mössbauer spectroscopy and powder X-ray diffraction (XRD). Results: ICP-MS showed iron in all magnetic samples, and some nickel and chromium. Mössbauer spectroscopy and XRD detected ferromagnetic minerals, particularly magnetite, followed by goethite and hematite. Conclusion: This original study of cosmetic ink stock products made with iron oxide pigments reports magnetic impurities in inks for cosmetic tattooing, e.g., magnetite, goethite, and hematite. These may be the main cause of MRI burn sensation in cosmetic tattoos. The mechanism behind sensations is hypothesized to be induction of electrical stimuli of axons from periaxonal pigment/impurity activated by magnetic force. Magnetite is considered the lead culprit.