Research refutes claims about the safety of nanoparticle-based sunscreens

It is prudent to put on sunscreen this summer – repeated doses – despite what you have read about the potential toxicity of sunscreens.

A new study conducted by the University of Queensland (UQ) and the University of Southern Australia (UniSA) provides the first direct evidence that zinc oxide nanoparticles used in sunscreens do not penetrate the skin and do not cause cellular toxicity after repeated applications.

The research, published this week in the Dermatology Journal of Investigation, refutes widespread claims among some advocacy groups – and growing consumer belief – about the safety of nanoparticle-based sunscreens.

Professor Michael Roberts, principal investigator of UQ and UniSA, said that the myth of sunscreen toxicity had taken root after previous animal studies had revealed a dermal absorption much higher sunscreens containing zinc than in human studies.

"It was feared that these nanoparticles of zinc oxide could be absorbed into the epidermis, with toxic consequences including DNA damage," said Professor Roberts.

The toxicity link has been echoed by consumers, raising fears that Australians will reduce their use of sunscreen, confirmed a national survey on sun protection led by the Cancer Council 2017 that showed a drop in the number of people who thought that it was safe to use sunscreen every day.

Professor Roberts and his co-investigators in Brisbane, Adelaide, Perth and Germany have studied the safety of repeated applications of zinc oxide nanoparticles applied to five volunteers aged 20 to 30 years.

The volunteers applied the ZnO nanoparticles every hour for six hours for five consecutive days.

"Using superior imaging methods, we established that the nanoparticles remained in the superficial layers of the skin and did not cause any cell damage," explains Professor Roberts.

"We hope that these results will help boost consumer confidence in these products and thus improve sun protection." The terrible consequences of skin cancer and skin damage caused by prolonged exposure to the sun are far greater than any toxicity caused by approved sunscreens. "