Where Is Zinc Oxide Found and What Is It Used For?

Zinc oxide shows up in an enormous range of products and industries, from the white paste lifeguards wear on their noses to the tires on your car. It is a white, powdery compound made of zinc and oxygen, and its combination of UV-blocking ability, chemical stability, antimicrobial properties, and semiconductor behavior makes it one of the most versatile metal oxides in commercial use. Most people encounter it daily without knowing it, because it is embedded in sunscreens, rubber goods, paints, ceramics, food packaging, animal feed, and electronics.

How Zinc Oxide Is Manufactured

Zinc oxide exists in nature as the mineral zincite, but natural deposits are far too small to meet industrial demand. Almost all zinc oxide on the market is manufactured, and two processes dominate production. Under the ISO 9298 standard, they are classified as the direct (American) process and the indirect (French) process.¹

In the direct process, zinc ore is heated with coal, which reduces it to zinc vapor. That vapor then reacts with oxygen in the same reactor to form zinc oxide particles. The whole cycle happens in one step, which keeps costs down but produces a somewhat less pure product. In the indirect process, metallic zinc is first melted in a furnace and vaporized at roughly 910 °C, then the zinc vapor immediately reacts with air to form zinc oxide.¹ Because the starting material is already refined metal, the French process yields a purer product, which matters for applications like pharmaceuticals and electronics where contaminants are a problem.²

A third route, the wet chemical process, synthesizes zinc oxide from zinc salt solutions and is especially useful when researchers need nanoparticles of a specific size or shape. This approach is more common in labs and specialty manufacturing than in bulk production.

Properties That Make It So Useful

Zinc oxide is a semiconductor with a wide band gap, meaning it absorbs ultraviolet light while letting visible light pass through. It is roughly 85% transparent in the visible spectrum, which is why sunscreens made with it do not look as opaque as you might expect from a white powder.³ It is also piezoelectric, generating a tiny voltage when mechanically stressed, and it shows strong chemical and thermal stability. On top of that, it has natural antimicrobial activity against a range of bacteria and fungi. Few single materials combine optical, electrical, mechanical, and biological properties in one package, which is why zinc oxide keeps finding new applications decade after decade.

Sunscreen and UV Protection

Zinc oxide is one of only two mineral UV filters widely approved for sunscreen use (the other being titanium dioxide). For years, people assumed these mineral sunscreens work by physically reflecting UV rays off the skin, like tiny mirrors. Research has overturned that idea. Across the UV spectrum, zinc oxide and titanium dioxide reflect only about 4 to 5% of UV radiation, far too little to explain their protective effect. The real mechanism is absorption: the semiconductor band gap of zinc oxide absorbs UV photons before they can reach living skin cells.⁴ The reflection people associate with mineral sunscreens actually happens at longer wavelengths in the visible range, which is what creates the white cast.

One practical advantage zinc oxide has over many chemical UV filters is its broad-spectrum coverage. It attenuates UV radiation across both the UVB and UVA ranges, including the long-wavelength UVA I region that most chemical filters handle poorly. It is also photostable, meaning it does not break down when exposed to sunlight the way some organic sunscreen ingredients do, and it does not react with other sunscreen actives under irradiation.⁵

Are Zinc Oxide Nanoparticles in Sunscreen Safe

Modern sunscreens often use nanoparticle-sized zinc oxide to reduce the visible white film on skin. This has raised safety questions, because nanoparticles are small enough, in theory, to penetrate the skin barrier. Lab studies on isolated cells have shown that zinc oxide nanoparticles can cause cellular and genetic damage under certain conditions, and some have been detected in deeper skin layers during long-term exposure experiments.⁶

However, the evidence from human volunteers tells a more reassuring story. In a study where nanoparticle zinc oxide sunscreen was applied repeatedly to real skin, the particles accumulated on the skin surface and within skin furrows but did not penetrate into the living layers of the epidermis and did not cause toxicity in those deeper cells. Zinc ions (dissolved from the particles) did penetrate into the skin, but this too did not appear to cause local damage.⁷ The gap between cell-culture results and real-skin results makes sense: intact human skin is a formidable barrier, and what harms a cell in a petri dish may never reach a living cell on your body.

The Rubber and Tire Industry

If you had to name the single largest industrial consumer of zinc oxide, it would be the rubber industry. Zinc oxide is the best-known cure activator for sulfur-based vulcanization, the chemical process that turns raw rubber into the elastic, durable material used in tires, hoses, belts, and seals.⁸ Without it, sulfur cross-linking is slow and inefficient, producing rubber with inferior mechanical properties. The compound works in both natural rubber and synthetic variants like polybutadiene.⁹

There is a catch: zinc oxide is classified as highly toxic to aquatic organisms, and the sheer volume used in rubber manufacturing means significant quantities eventually wash into waterways through tire wear and industrial discharge.⁸ This has pushed researchers to find ways to use less of it. One promising approach uses a hierarchically structured form of zinc oxide built from nanoparticles assembled into micron-sized platelets. Rubber compounds made with this material retained comparable mechanical performance and scorch safety even when the zinc oxide content was cut by up to 90%.¹⁰

Paints, Coatings, and Corrosion Protection

Zinc oxide has been used as a white pigment in paints for centuries. Today its pigment role is less dominant because titanium dioxide largely replaced it for whiteness and opacity, but zinc oxide still earns its keep in protective coatings. In zinc-rich primers used to protect steel, adding zinc oxide creates a dual defense: metallic zinc particles provide cathodic protection (they corrode sacrificially instead of the steel), while zinc oxide adds a physical barrier that blocks corrosive agents. Researchers found the best corrosion resistance in primers loaded with about 15% zinc oxide by weight alongside metallic zinc dust.¹¹

More recent work has explored vegetable-oil-based coatings containing zinc oxide as a sustainable alternative to paints that rely on heavy metal pigments. These coatings showed lower corrosion current density and stronger impedance response than uncoated steel, and in some assessments outperformed commercial products built around traditional heavy-metal formulations.¹²

Medical and Dental Uses

Zinc oxide has been a staple of wound care for generations. Calamine lotion, diaper-rash cream, and many over-the-counter skin protectants list it as an active ingredient. Its mild antiseptic and astringent properties help soothe irritated skin, and it forms a physical barrier against moisture. In animal studies, a topical zinc oxide formulation improved early wound closure and collagen-related measures during the first week of healing, though the differences between treated and untreated wounds narrowed by two and three weeks.¹³

In dentistry, zinc oxide shows up in temporary fillings, root canal sealers, and luting cements. Zinc oxide eugenol (a mix of zinc oxide with clove oil extract) has been a go-to temporary filling material for decades. The long-standing advice was to avoid placing composite resin restorations directly over a zinc oxide eugenol base, because eugenol was thought to soften the composite. More recent testing challenges that idea: several modern composites actually showed better hardness values when placed over a zinc oxide eugenol base than without one, suggesting the old rule may no longer hold for current materials.¹⁴ Long-term clinical follow-ups of restorations cemented with zinc oxide eugenol have also found no significant difference in success rates compared with zinc phosphate cement after four to seven years.¹⁵

Electronics and Electrical Protection

Zinc oxide’s semiconductor properties make it valuable in electronics. One of its biggest roles is in varistors, which are voltage-dependent resistors used in surge arresters to protect power grids and electronic equipment from voltage spikes. The zinc oxide in a varistor has nonlinear electrical characteristics: it conducts very little current under normal voltage but instantly absorbs large surges of energy. Doping zinc oxide with small amounts of other elements like gallium can further reduce leakage current and improve stability under repeated high-charge events.¹⁶

Zinc oxide also finds use in UV photodetectors, transparent conductive films for touchscreens and displays, and light-emitting diodes. Its wide band gap and high exciton binding energy make it a natural fit for optoelectronic devices that need to operate in the ultraviolet part of the spectrum.³

Animal Feed and Agriculture

Zinc oxide has long been added to piglet diets at high doses during the stressful post-weaning period. The transition from sow’s milk to solid feed often causes gut inflammation and diarrhea in young pigs, and pharmacological-level zinc oxide supplementation (around 3,000 mg per kg of feed) helps smooth that transition. In a recent trial, piglets receiving zinc oxide gained about a third more weight per day than control animals and had more consistent feces. The mechanism appears to involve reduced expression of inflammatory signals and pathogen-recognition proteins in the gut lining, essentially calming the intestinal immune response so the piglet can absorb nutrients more efficiently.¹⁷

Even at lower doses, specialized forms like porous or nano-structured zinc oxide improved piglet growth performance, strengthened intestinal barrier function, and shifted gut microbial communities in favorable directions.¹⁸ The European Union, however, banned the high-dose use of zinc oxide in pig feed in 2022 over concerns about antimicrobial resistance and environmental zinc accumulation. This has created a race to find lower-dose alternatives or novel zinc oxide forms that deliver the same gut benefits with less environmental baggage.

Food Packaging

The antimicrobial properties of zinc oxide are being harnessed for active food packaging. By embedding zinc oxide nanoparticles into biodegradable films, researchers have created wraps that extend the shelf life of perishable foods. In one study, films containing zinc oxide nanoparticles alongside cellulose nanofibers significantly reduced bacterial counts on chicken fillets compared with conventional plastic packaging, with particular effectiveness against gram-positive bacteria.¹⁹ Zinc oxide nanoparticles are also being studied as a zinc fortification source for processed foods, though they need to be encapsulated in protein-pectin complexes to improve stability and bioavailability when consumed.²⁰

Water Treatment and Pollution Cleanup

When zinc oxide absorbs UV light, it generates reactive oxygen species on its surface that break down organic pollutants. This photocatalytic property has attracted significant interest for water treatment. Under UV illumination, zinc oxide degraded about 98% of 4-nitrophenol, a common industrial pollutant, in just 90 minutes.²¹ Silver-zinc oxide composites have pushed performance even further: one nanocomposite degraded roughly 83% of Congo red dye in 20 minutes under a low-power LED light source, with the breakdown driven by superoxide radicals, hydroxyl radicals, and photogenerated holes on the catalyst surface.²²

Gas Sensing

Zinc oxide’s surface chemistry changes measurably when it comes into contact with various gases, which makes it a strong candidate for chemical sensors. The sensing mechanism relies on oxygen molecules that cling to the zinc oxide surface and react with volatile organic compounds, altering the material’s electrical resistance in proportion to gas concentration.²³ Zinc oxide nanorod sensors have demonstrated striking sensitivity to ammonia vapor at room temperature, with responses thousands of times above baseline, and UV illumination improves their detection sensitivity further.²⁴ The practical appeal is a sensor that works at room temperature and can be activated with inexpensive LED light, avoiding the high operating temperatures older metal-oxide sensors required.

Solar Cells and Emerging Technologies

Zinc oxide nanowires are being explored as an electron-transport layer in flexible perovskite solar cells. These cells are thinner, lighter, and potentially cheaper to manufacture than rigid silicon panels. Since the first report of a zinc oxide nanowire perovskite cell achieved about 2.6% power conversion efficiency in 2013, the technology has improved to roughly 15%.²⁵ That is still behind mainstream silicon panels, but the pace of improvement has been rapid, and the flexibility advantage opens applications on curved surfaces, portable devices, and building facades where rigid panels cannot go.

Zinc oxide coatings on textiles represent another frontier. Cotton fabrics treated with zinc oxide nanoparticles anchored to a polydopamine template achieved a UV protection factor above 120 and maintained 99% reduction in bacterial load even after five washing cycles.²⁶ That durability through laundering has been a persistent challenge for functional textile coatings, and the polydopamine anchoring approach appears to solve it for zinc oxide.

Occupational Hazards and Metal Fume Fever

While zinc oxide is generally considered safe in products like sunscreens and ointments, breathing in its fumes is a different story. When zinc or zinc alloys are heated above roughly 500 °C during welding, galvanizing, or smelting, zinc oxide forms as a fine aerosol. Inhaling those particles causes metal fume fever, an acute illness with flu-like symptoms including chills, fever, muscle aches, and malaise that typically onset a few hours after exposure.²⁷ The condition is common among welders and galvanizing workers. It is usually transient and resolves on its own within a day or two, but repeated episodes are unpleasant, and animal studies suggest that heavy nanoparticle inhalation can trigger acute lung injury involving inflammation and disrupted cellular cleanup processes.²⁸ Proper ventilation and respiratory protection are the standard defenses in occupational settings.

Environmental Concerns in Water and Marine Ecosystems

The same properties that make zinc oxide antimicrobial and photocatalytically active create risks when the compound enters natural waters. In aquatic environments, zinc oxide particles dissolve relatively quickly, releasing zinc ions. Those ions, rather than the particles themselves, appear to drive most of the toxic effects on aquatic organisms, and the size of the original particles makes little difference.²⁹

Marine ecosystems may be especially vulnerable. Exposure to zinc oxide nanoparticles suppresses the growth and photosynthesis of symbiotic algae that live within coral tissue, a finding with alarming implications for coral reef health. The affected algae showed signs of oxidative stress and downregulation of essential photosynthetic proteins, both of which could weaken the algae-coral partnership that keeps reefs alive.³⁰ This has led to calls for incorporating nanomaterial monitoring into coastal environmental assessments, particularly in reef-adjacent areas with heavy sunscreen use or industrial discharge.