Q-switch laser and tattoo pigments: first results of the chemical and photophysical analysis of 41 compounds.

In the Western world, there are at least 20-30 million people with tattoos. Improved self-image and social stigmatization are the main reasons for removing tattoos from skin. Q-switched lasers are applied to destroy the tattoo compounds in the skin. The treatment of tattoos containing ink often gives excellent results, whereas the results of treatments for coloured tattoos are not predictable and usually are worse. The chemical structure and the absorption spectra of the tattoo pigments are usually unknown. However, the efficacy of the treatment by using light of different Q-switched lasers (wavelengths 510, 532, 694, 755, 1064 nm) is correlated to both the chemical structure of the tattooed compounds yielding specific absorption spectra and the laser wavelength used. A structural and spectroscopic analysis of 41 coloured pigments was performed. The 41 substances were identified, and they consist of 16 individual chemicals of different structured well-known industrial organic pigments. The absorption spectra of the 16 pigments were measured quantitatively. The results of the present analysis explain to some extent the outcome of clinical studies regarding laser therapy of coloured tattoos. Because the laser energy used produces a high temperature in the azo or polycyclic pigments, it is necessary to investigate whether that change causes possibly toxic or cancerogenic compounds.