Zinc Oxide
Also known as Zinc Oxide, ZnO, Zinc White, Flowers of Zinc
“EU CosIng says: restricted.”
Zinc oxide (CAS 1314-13-2) is a broad-spectrum inorganic UV filter (UVA + UVB) approved at up to 25% in both the EU (Annex VI, entries 30 and 30a) and the US (21 CFR § 352.10(r)). Both jurisdictions prohibit use in spray/aerosol forms that may cause pulmonary inhalation. CIR has not issued a safety assessment for zinc oxide; the ingredient is absent from both the 12/2017 and Oct 2024 QRTs, as CIR formally defers to FDA for OTC drug-active ingredients. The 2017 risk assessment (Kim et al., PMID 28509652) established a NOAEL of 268.4 mg/kg/day and calculated a margin of safety of 448 at the 25% regulatory limit, concluding safe cosmetic use. The 2009 review (Newman et al., PMID 19646780) found no evidence of significant penetration of nanosized zinc oxide beyond the stratum corneum in intact skin. The 2022 study (Chen et al., PMID 34983566) found that zinc oxide nanoparticles combined with UVB activate NLRP3 inflammasome-mediated pyroptosis in keratinocytes under experimental conditions; this signal is specific to nano form with concurrent UV exposure and is not considered a systemic safety concern at current cosmetic use levels.
Broad-spectrum UV protection covering both UVA and UVB wavelengths; one of only two mineral UV filters with recognized broad-spectrum activity (along with titanium dioxide)
Approved at up to 25% in the US and EU — the highest concentration ceiling of any sunscreen active ingredient in either jurisdiction
Inorganic/mineral UV filter with low systemic absorption; unlike organic UV filters, does not undergo chemical degradation or photoisomerization under UV exposure
Long history of safe use in cosmetics including in baby and sensitive-skin products; no established carcinogenicity or genotoxicity in standard battery tests
NOAEL of 268.4 mg/kg/day with margin of safety of 448 at 25% use concentration; no adverse effects reported in multiple animal toxicity studies
Inhalation risk: both EU Annex VI entries (30 and 30a) and FDA OTC monograph prohibit use in spray/aerosol applications that may cause lung exposure; the restriction applies to both nano and non-nano forms
Nano-form distinction: EU Annex VI treats non-nano (entry 30) and nano (entry 30a) as separate regulatory entries with identical concentration caps but more detailed physicochemical specifications for the nano form (purity, crystalline structure, particle size, water solubility, permitted coatings)
Nano ZnO + UVB co-exposure: in vitro and in vivo study found NLRP3 inflammasome activation and pyroptosis in keratinocytes under combined ZnO nanoparticle + UVB conditions; relevance to real-world sunscreen use (where ZnO absorbs UVB) requires further characterization
CIR has issued no safety assessment for zinc oxide as a cosmetic ingredient — the ingredient is absent from both the 2017 and 2024 CIR Quick Reference Tables; CIR defers to FDA for OTC drug-active ingredients
- · 25% Not to be used in applications that may lead to exposure of the end-user's lungs by inhalation. (EU Regulation 1223/2009 Annex VI, entry 30 — non-nano form only.)
- · 25% Not to be used in applications that may lead to exposure of the end-user's lungs by inhalation. Nano form only: purity ≥96%, wurtzite crystalline structure, median particle size D50 >30 nm and D1 >20 nm, water solubility <50 mg/L; may be uncoated or coated with permitted silane compounds or dimethicone. (EU Regulation 1223/2009 Annex VI, entry 30a — nano form.)
EU Regulation 1223/2009 Annex VI — UV filters (consolidated), entries 30 (Zinc oxide, non-nano) and 30a (Zinc oxide, nano): max 25%, inha…
“Not to be used in applications that may lead to exposure of the end-user's lungs by inhalation.”— EU Regulation 1223/2009 Annex VI, entry 30 (Zinc oxide, non-nano), conditions column
21 CFR Part 352 — OTC Sunscreen Drug Products (govinfo.gov consolidated XML, § 352.10(r)): Zinc oxide up to 25 percent
“Zinc oxide up to 25 percent.”— 21 CFR Part 352, § 352.10(r)