How Zinc Oxide Works as a Physical UV Filter

Zinc oxide works as a physical UV filter by scattering and reflecting UV radiation across both UV-A (315–400 nm) and UV-B (280–315 nm), providing true broad-spectrum protection with a critical wavelength of approximately 385–390 nm. Indo Lysaght supplies pharmaceutical-grade zinc oxide (≥99.7%) certified under GMP ISO 22716, Halal, and REACH for sunscreen manufacturers requiring compliant, batch-tested ingredient supply. 

Physical vs Chemical UV Filters: Two Fundamentally Different Mechanisms

UV filters fall into two categories based on how they interact with ultraviolet radiation:

·       Physical (mineral) filters, zinc oxide and titanium dioxide: work by scattering and reflecting UV radiation away from the skin surface. They are photostable, do not penetrate significantly into skin, and generate minimal reactive oxygen species (ROS) upon UV exposure

·       Chemical (organic) filters, avobenzone, octinoxate, oxybenzone, DHHB: absorb UV radiation and convert it into heat. They can degrade under prolonged UV exposure (photodegradation), some have skin penetration concerns, and some generate ROS upon absorption

The practical implication: physical filters like zinc oxide provide broad-spectrum protection without chemical breakdown in sunlight. This makes them preferred for sensitive skin formulations, infant sunscreens, reef-safe products, and long-wear outdoor applications where coating stability is critical.

ZnO's Unique UV-A Advantage: True Broad-Spectrum Coverage

Not all UV filters cover the same wavelength range. The UV spectrum is divided into UV-B (280–315 nm) and UV-A, which is further split into UV-A2 (315–340 nm) and UV-A1 (340–400 nm). UV-A1, the longest wavelength UV radiation, penetrates deepest into the dermis and is the primary driver of photoaging, hyperpigmentation, and certain skin cancers.

FDA and EU regulators define 'broad-spectrum' as a critical wavelength of ≥370 nm, meaning the filter must offer measurable protection into the UV-A1 range. Zinc oxide achieves a critical wavelength of approximately 385–390 nm, well above the 370 nm threshold, covering the full UV-A spectrum.

Titanium dioxide achieves a critical wavelength of approximately 340–360 nm, covering UV-B and UV-A2 but offering limited protection in UV-A1 (above 360 nm). This is why formulations using TiO2 alone cannot always meet broad-spectrum claims without adding a UV-A absorbing chemical filter. Zinc oxide, used alone at sufficient concentration, can meet broad-spectrum claims in most markets.

Particle Size and SPF Contribution

Zinc oxide particle size affects both cosmetic elegance and SPF contribution:

·       Non-nano ZnO (particle size >100 nm, including Indo Lysaght Pharmaceutical grade powder): produces visible white cast on skin. Preferred in clean beauty formulations and for buyers requiring explicit non-nano ingredient labeling. SPF contribution at 10% ZnO concentration: approximately SPF 15–20

·       Nano ZnO (primary particle size <100 nm): disperses transparently in formulation with minimal white cast. Higher SPF efficiency per gram due to larger surface area. At 8–12% concentration: approximately SPF 20–35

SPF values are formulation-dependent and must be confirmed by in vivo testing per ISO 24444 or FDA protocol before any SPF label claim. The reference values above are estimates for formulation planning purposes only.

For non-nano pharmaceutical-grade zinc oxide from Indo Lysaght (Pharmaceutical grade, ≥99.7%): SPF contribution at 15% concentration in standard emulsion formulation is approximately SPF 25–30, confirmed by ISO 24444 testing. Contact cs@indolysaght.com for formulation development support.

Regulatory Status by Market

Across all major regulatory markets, zinc oxide as a sunscreen active requires pharmaceutical-grade purity (≥99.7%) from a GMP-certified supplier, with per-batch CoA documentation. Halal certification from the ZnO supplier is additionally required for products sold in Muslim-majority markets including Indonesia, Malaysia, and Gulf states.

Case Study

The following is a hypothetical illustration. All figures, processes, and technical details reflect real operating terms. The profile is entirely fictional and does not represent any real individual.

Profile:  Sarah Purnama, 35, Formulation Chemist, halal cosmetics company, Bandung.

Project:  First mineral sunscreen product. SPF 30, broad-spectrum, Halal supply chain. Target markets: Saudi Arabia (SFDA) and Malaysia (NPRA).

Condition / Problem:

·       Requirement 1: SPF 30 + critical wavelength ≥370 nm using non-nano pharmaceutical ZnO, no prior mineral sunscreen experience in-house

·       Requirement 2: SFDA and NPRA require supplier to hold GMP ISO 22716, JAKIM-recognized Halal, and REACH registration

·       Requirement 3: 4-month timeline from ingredient qualification to BPOM submission, no room for supplier re-qualification delays

Solution:

·       Qualified Indo Lysaght Pharmaceutical-grade ZnO: purity ≥99.7%, Halal MUI (JAKIM-recognized, 2017), GMP ISO 22716 (2017), REACH (2018)

·       Sample CoA received in 5 days. ZnO 99.7% (specific decimal); formulation work began immediately

·       ZnO at 15% concentration in standard O/W emulsion submitted for ISO 24444 in vivo SPF testing

Result:

·       ISO 24444 in vivo SPF result: 32.4 (above SPF 30 label claim)

·       Critical wavelength: 389 nm (broad-spectrum confirmed, above 370 nm threshold per FDA/EU/BPOM)

·       BPOM cosmetics notification: approved on first submission

·       Saudi Arabia SFDA: approved within 8 weeks  |  Malaysia NPRA: approved, Halal MUI accepted by JAKIM

·       First production run: 3,000 finished units + 200 kg ZnO ingredient

When to Contact an Expert Supplier

Contact Indo Lysaght's technical team for pharmaceutical-grade zinc oxide sourcing guidance if:

·       Your sunscreen formulation requires a broad-spectrum claim and your current UV filter blend uses TiO2 alone without meeting the 370 nm critical wavelength threshold

·       Your product targets export to Muslim-majority markets and your ZnO supplier does not have Halal certification

·       You need per-batch AAS CoA documentation for FDA or EU regulatory submission, not just periodic test certificates

·       You are reformulating from a chemical UV filter system to a mineral system for a clean beauty or reef-safe positioning

Conclusion

·       Zinc oxide is the only single-ingredient physical UV filter capable of meeting broad-spectrum claims across most regulatory markets, due to its critical wavelength of ~385–390 nm covering the full UV-A spectrum (315–400 nm)

·       TiO2 (critical wavelength: ~340–360 nm) offers UV-B and UV-A2 protection but requires additional UV-A absorbing co-ingredients for broad-spectrum compliance. ZnO does not

·       For all sunscreen applications, specify Pharmaceutical-grade ZnO (≥99.7%, GMP ISO 22716, Halal, REACH) with per-batch AAS CoA, this is the supplier documentation standard across all major regulatory frameworks

Frequently Asked Questions

Q: What wavelengths does zinc oxide protect against as a UV filter?

A: Zinc oxide provides broad-spectrum UV protection covering UV-B (280–315 nm) and the full UV-A range: UV-A2 (315–340 nm) and UV-A1 (340–400 nm). Its critical wavelength of approximately 385–390 nm exceeds the FDA and EU broad-spectrum threshold of 370 nm. This makes ZnO the only single-ingredient physical UV filter that can meet broad-spectrum claims across major regulatory markets without combining with additional UV-A absorbers.

Q: How is zinc oxide different from titanium dioxide as a UV filter?

A: Both zinc oxide and titanium dioxide are physical UV filters that scatter and reflect UV radiation. The key difference is UV-A coverage: ZnO has a critical wavelength of ~385–390 nm, protecting across the full UV-A1 range (340–400 nm). TiO2 has a critical wavelength of approximately 340–360 nm, providing good UV-B and UV-A2 protection but limited UV-A1 coverage. TiO2 formulations typically require an additional chemical UV-A absorber to achieve broad-spectrum compliance.

Q: What concentration of zinc oxide achieves SPF 30?

A: Non-nano pharmaceutical-grade zinc oxide at approximately 15–18% concentration in a standard O/W emulsion formulation typically achieves SPF 25–35 (formulation and vehicle dependent). Nano zinc oxide achieves similar SPF at 8–12% due to higher surface area efficiency. All SPF values must be confirmed by in vivo testing per ISO 24444 or FDA OTC protocol before any SPF claim on finished product labels.

Q: What is the difference between nano and non-nano ZnO for sunscreen?

A: Nano zinc oxide (primary particle size <100 nm) disperses transparently in formulations with minimal white cast, offering cosmetic elegance at lower concentrations. Non-nano zinc oxide (>100 nm), including Indo Lysaght Pharmaceutical-grade powder, produces visible white cast but is preferred in clean beauty and non-nano-labeled formulations. Both require ≥99.7% purity from a GMP-certified supplier for sunscreen applications regulated under FDA, EU, or BPOM frameworks.

Q: What supplier certifications are required for global sunscreen ZnO supply?

A: For global sunscreen supply, a zinc oxide supplier must hold: GMP ISO 22716 (required by EU and aligned markets), Halal certification (required for Muslim-majority markets. Indonesia, Malaysia, Saudi Arabia, UAE), REACH registration (required for EU-linked supply chains), and ISO 9001 for quality management. Indo Lysaght obtained all four certifications: GMP 2017, Halal 2017, REACH 2018, ISO 9001 1999 (updated 2015). Each batch includes per-batch AAS CoA showing purity ≥99.7%.