Titanium dioxide has been an effective and safe physical sunblock for decades. In recent years, nanoparticle versions of titanium dioxide have become more popular and raised questions regarding potential safety risks. According to findings published in Jama Dermatology, Sergio G. Coelho, Ph.D., and his team measured the number of titanium dioxide particles on the skin, depth of skin penetration, and irritation after repeated application. The researchers applied sunscreens with and without titianium dioxide particles on their small group of participants. After the final sunscreen application, five shave biopsy specimens were taken from each subject—two from the sunscreen plus titanium dioxide; two from the sunscreen only sites; and one from the control. Then, they used a transmission electron microscopy to evaluate penetration of the titanium dioxide particles through the epidermal and dermal skin layers, which were identified via scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX).
As expected, the skin sites that received sunscreen plus titanium dioxide nanoparticles contained more titanium dioxide than control sites and those treated with sunscreen only. The nanoparticles were mainly present in low levels in the dermis surround hair follicles. None of the participants experienced irritation or other side effects at the application sites. “Our findings depend on selected ‘regions of interest,’ which does not allow a detailed quantitative assessment of dermal penetration of TiO2 nanoparticles,” says Coehlo. “Notwithstanding its limitations, however, it provides valuable data on the dermal penetration of titanium dioxide nanoparticles and the parameters for informing the design of future clinical studies.”