What it is
Zinc oxide is an inorganic compound, ZnO, a white powder that is insoluble in water and serves as a mineral (inorganic) sunscreen filter. It protects across the ultraviolet range, covering UVB and both UVA II and UVA I, which makes it one of the broadest-spectrum single filters available. As an inorganic filter it is completely photostable, meaning it does not break down under sunlight the way some chemical filters can. Beyond sun protection it also acts as a skin protectant and is used in products such as barrier creams.
Spectrum coverage
UVA1 · UVA2 · UVB
Regional approval · max %
Safety & warnings
Zinc oxide is regarded as one of the gentlest UV filters and is widely described as nonirritating, nonallergenic, and non-comedogenic, which is why it is common in products for sensitive skin and in baby barrier creams for diaper rash. Its main cosmetic drawback is the visible white cast it can leave, which manufacturers reduce with finer particle sizes; safety reviews have focused mainly on avoiding inhalation of loose powder or spray forms rather than on standard topical creams.
Origin & sourcing
Zinc oxide is manufactured chiefly by two routes. In the French (indirect) process, metallic zinc is melted and vaporized near 1000 degrees Celsius and reacts with oxygen in the air to form ZnO particles collected as they cool. The American (direct) process starts from zinc-bearing ores or smelter byproducts heated with carbon, giving a lower-purity product.
History
Zinc oxide has a long history in skin care: the Indian medical text the Charaka Samhita, thought to date from around 500 BC or earlier, mentions a salve probably made of zinc oxide for eyes and wounds. Around 1782 Louis-Bernard Guyton de Morveau proposed it as a non-toxic replacement for lead white pigment, and as zinc white it became widely used in oil painting by the mid-1800s because it resists sunlight and sulfur-bearing air. A version blended with iron oxide is the basis of calamine lotion.
Questions everyone asks
How does zinc oxide protect skin from the sun?
It is a mineral UV filter that sits on the skin and provides broad-spectrum protection across UVB and UVA, and it is photostable so it does not degrade in sunlight.
Why does zinc oxide leave a white cast?
Zinc oxide is a white powder, so it can leave a whitish tint; manufacturers use finer particle sizes to reduce how visible it is on the skin.
Is zinc oxide good for sensitive skin?
It is widely considered nonirritating, nonallergenic, and non-comedogenic, which is why it is often chosen for sensitive skin and used in baby barrier creams.