Is Sunscreen Safe? Study tests zinc oxide for skin penetration

Is Sunscreen Safe Study tests zinc oxide for skin penetration

A study published in Cosmetics ​tested the stability and skin penetration of two types of zinc oxide, following recent concerns regarding the safety of this ingredient. The authors found that both types of zinc oxide tested did not penetrate the skin to the deepest layers.

The authors used 20% coated zinc oxide and 20% uncoated zinc oxide nanoparticles. The penetration was assessed via confocal laser microscopy.


There are two different types of sunscreens: physical ones that use inorganic filters, and chemical ones that use organic filters. Only zinc oxide and titanium dioxide are approved for use as physical sunscreens, which help to reflect or scatter UV light. The alternative, organic filter sunscreens, often have poor spreadability and other appearance concerns.

The use of nanoparticulate formations creates transparent sunscreen formulations, which is desirable to most consumers. However, in prior studies zinc oxide nanoparticles have had more adverse effects on keratinocytes than titanium dioxide. These effects include disruption of mitochondrial function, the production of reactive oxygen species and oxidative DNA damage, along with genotoxic potential within epidermal cells.

It is worth noting that most studies analyze sunscreens available on the market rather than the key ingredients, leading to uncertainty regarding which ingredient may be causing issues. The authors of this study made a simple sunscreen formulation in order to test zinc oxide itself, rather than other active and inactive ingredients found in sunscreens.

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