Optimising Laser Tattoo Removal: A Comprehensive Analysis of Parameters, Techniques, and Safety Protocols

Abstract

Tattoos have become increasingly popular as a means of cultural identity and self-expression, leading to a corresponding rise in tattoo removal procedures. Despite this growing trend, concerns about the chemical composition of tattoo inks and the safety of laser removal treatments remain insufficiently addressed. This thesis investigates the chemical and toxicological implications of laser tattoo removal, with particular emphasis on the transformation of ink constituents under laser exposure. Chapter One provides a comprehensive review of the history of tattooing, ink composition, and laser- based tattoo removal techniques. It also discusses related health concerns, as well as the chemical and cytotoxic profiles of tattoo inks and their laser degradation by-products. Chapter two evaluated the components of commercially available tattoo inks (LY, GY, GR, BO and reference pigments PY14, PY65, PO13, PB15). Through analysis and using range of analytical techniques, including IR, NMR, XRD, Raman, EDX-SEM and ICP-OES, the components were identified. It was discovered that several of the tattoo inks studied were mislabelled, containing undeclared pigments and additional elements not listed on their bottle labels or safety data sheets. These new findings highlight significant inconsistencies in labelling practices, raising concerns about consumer safety, regulatory oversight, and the transparency of tattoo ink manufacturers. The presence of unlabelled components in inks suggests the potential for unknown health risks and underscores the need for stricter regulations and monitoring of the tattoo ink industry. Certain tattoo inks are resistant to removal using laser methods because of their composition. This includes the removal of yellow pigments and tattoo inks containing titanium dioxide (TiO2). Research outlined in chapter three describes a novel study focused on advancing the understanding of tattoo pigment photodegradation by investigating how TiO₂, a common additive in tattoo inks, influences the degradation of yellow pigments under 532 nm laser light. This study investigated several yellow pigments and tattoo inks before and after exposure to 532 nm QS Nd:YAG laser irradiation. A variety of analytical techniques were employed, including EDX-SEM, DLS, XRD, and GC-MS, to characterise the pigments and their degradation products. Results indicated that TiO₂ alters the degradation pathway, forming large particle agglomerates with ink components. This interaction reduced the amount of evolved of volatile fragments during laser irradiation, which could have implications for the effectiveness of tattoo removal and the safety of the degradation by-products. The behaviour of TiO₂ in tattoo inks provides valuable insights into the challenges of laser tattoo removal and the complexity of pigment interactions during the process. In addition, some of the degradation products were identified to be potentially harmful to the human body. v Chapter four addressed a critical gap in the literature by exploring the effects of laser treatments on tattooed dark skin. Melanin, a natural pigment abundant in darker skin tones, was found to interfere with laser therapies, leading to suboptimal results. The study specifically investigated the degradation of yellow pigments in the presence of melanin under laser irradiation. Yellow tattoo inks, reference pigments, and pigment-melanin mixtures were treated with a 532 nm QS Nd:YAG laser. The resulting degradation products, as well as their morphology and particle size, were analysed using GC-MS, SEM, and DLS. Findings revealed that melanin behaves similarly to TiO₂, altering pigment degradation pathways and reducing the formation of volatile fragments. These results provide a better understanding of the interaction between tattoo pigments and melanin, offering insights into the challenges faced during laser tattoo removal on darker skin tones and emphasizing the need for tailored treatment protocols. Chapter five of this project used GC-MS to identify the degradation products formed on the irradiation of yellow pigments and inks. The chapter reports the formation o-toluidine, 2-methoxyphenyl isocyanate, and o-toluene isocyanate, compounds that have not been reported previously for these pigments. These compounds and the inks were assessed for their cytotoxic effects on HaCaT skin cells as breakdown products of tattoo inks and is one of the first cytotoxicity assessments of this kind. Experimental results showed that unirradiated inks and pigments reduced cell viability to approximately 50%, indicating inherent toxicity even before laser treatment. However, irradiated ink samples exhibited significantly heightened toxicity, with higher concentrations causing severe cell death. These findings underscore the potential health risks associated with both the use of tattoo inks and their breakdown during laser removal, raising concerns about the long-term safety of these practices. In conclusion, this study further advances the analytical understanding of tattoo inks and their laser- induced transformation. The findings emphasize the urgent need for improved regulatory standards for tattoo inks, greater awareness of the health implications of tattooing and laser removal, and the development of safer practices in the tattoo industry. Through the application of analytical techniques this research contributes valuable insight into pigment behaviour under laser irradiation particularly regarding challenges associated with darker skin tones and lays a scientific foundation for future investigations into the chemical safety and efficacy of tattoo removal technologies.