MINERAL
Zinc Oxide
A mineral UV filter used in sunscreens, which sits on the skin's surface rather than being absorbed into it.
Source
Mineral compound, manufactured from zinc metal or zinc ore
Used for
Mineral UV filter in sun care
How it works
Zinc oxide is a naturally occurring mineral compound that has been used in skin protection for centuries, from traditional skin care to today's sunscreens. In modern sun care, it's milled into an extremely fine, inert white powder that sits on the skin's surface as a physical UV filter rather than being absorbed into it.
For a long time it was assumed zinc oxide worked mainly by reflecting UV rays like a mirror, but research shows its real mechanism is absorption: the mineral's own semiconductor structure absorbs UV photons before they reach the skin, which is how it works as a UV filter. It's also photostable: unlike some other UV filters, it doesn't break down or lose effectiveness with continued sun exposure.
As a mineral sunscreen filter, zinc oxide should be applied generously as the last step of a morning routine, after moisturiser, and reapplied through the day with continued sun exposure. No SPF product, physical or chemical, holds up to its labelled protection without reapplication.
For a long time it was assumed zinc oxide worked mainly by reflecting UV rays like a mirror, but research shows its real mechanism is absorption: the mineral's own semiconductor structure absorbs UV photons before they reach the skin, which is how it works as a UV filter. It's also photostable: unlike some other UV filters, it doesn't break down or lose effectiveness with continued sun exposure.
As a mineral sunscreen filter, zinc oxide should be applied generously as the last step of a morning routine, after moisturiser, and reapplied through the day with continued sun exposure. No SPF product, physical or chemical, holds up to its labelled protection without reapplication.
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A mineral UV filter used in sunscreens
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Physically stable in sunlight, unlike some other UV filters
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Sits on the skin's surface rather than being absorbed, making it well suited to sensitive skin
Questions
Does zinc oxide work by reflecting sunlight?
Mostly not. Zinc oxide is often described as a reflective 'physical' filter, but a laboratory study that measured how much UV light passed through and bounced off films of zinc oxide and titanium dioxide found they reflected only a small fraction of it. Their main way of filtering UV is absorption, which comes from the semiconductor structure of the mineral itself. (Cole et al., 2016)
What is the difference between zinc oxide and titanium dioxide?
They are the two mineral UV filters used in sunscreens, and they cover different parts of the spectrum. A review of the two notes that titanium dioxide is more effective in the UVB range and zinc oxide in the UVA range, which is why they are often combined in mineral sunscreens. Very fine particles of either are used to reduce the white, opaque look that larger particles leave on skin. (Smijs & Pavel, 2011)
Where it comes from
Zinc oxide is a white compound of zinc and oxygen, made into a fine white powder for skincare. (Kołodziejczak-Radzimska & Jesionowski, 2014)
Good to know
Apply a zinc oxide sunscreen generously as the last step of your morning routine, after moisturiser, and reapply through the day with continued sun exposure. It's photostable, so it won't break down in the sun, but no SPF holds up to its labelled protection without reapplication.
The research
- Smijs T.G. and Pavel S., "Titanium dioxide and zinc oxide nanoparticles in sunscreens: focus on their safety and effectiveness," Nanotechnology, Science and Applications, 2011 (opens in a new tab)
- Cole C, Shyr T, Ou-Yang H. Metal oxide sunscreens protect skin by absorption, not by reflection or scattering. Photodermatology, Photoimmunology & Photomedicine, 2016 (opens in a new tab)
- Kołodziejczak-Radzimska A, Jesionowski T. Zinc Oxide: From Synthesis to Application: A Review. Materials, 2014 (opens in a new tab)
