Chemical SPF Filters

No binding to estrogen or androgen receptors. Inactive in uterotrophic assay (Ashby 2001). Low systemic absorption due to high molecular weight. Photostable broad-spectrum UVA/UVB. EU-approved since early 2000s. FDA proposed GRASE in Dec 2025. The gold standard among chemical filters.

Approximately 0.01% of applied dose penetrates skin. No estrogenic, androgenic, or uterotrophic activity (Ashby 2001). Hybrid particulate filter (scatters + absorbs). Photostable broad-spectrum. EU-approved. Not FDA-approved.

Only 0.014% of applied dose found in urine (Benech-Kieffer 2003). Photostable UVA. No photomutagenicity. No increased skin cancer in mouse studies. FDA-approved via NDA for L'Oreal products. Limited availability due to proprietary status.

Photostable UVA/UVB. Minimal skin absorption reported. Works synergistically with Mexoryl SX. EU-approved. L'Oreal proprietary.

Primary UVA filter in most US sunscreens. Photounstable: loses ~36% absorbance after 1 hour in sunlight unless stabilised. Generates ROS (singlet oxygen) upon UV exposure. However: no estrogenic activity detected (Schlumpf 2001), low percutaneous absorption (<=0.59% of applied dose), and 2025 toxicology review found no clear toxicity markers. The photostability issue is the main concern, not endocrine disruption.

Systemic absorption exceeds FDA threshold (up to 5.8 ng/mL in Matta 2020). Very weak estrogenic potency (~1/2,000,000 of estradiol). ECHA requested fish sexual development test. Less concerning than oxybenzone/octinoxate but not fully exonerated. Data gaps remain for chronic exposure.

Plasma concentrations reached 23.1 ng/mL (46x the FDA threshold) in Matta 2020. Estrogenic and anti-androgenic effects in vitro (Schlumpf 2001). EU SCCS could not identify safe concentration for full-body use. EU restricted to 7.34% in facial products effective 2025. Not alarming at low concentrations, but the EU restriction reflects genuine regulatory concern.

UVB-only filter providing no UVA protection. Photosensitises formation of oxidised guanines via type I and II mechanisms after UV exposure (Bastien 2010). Generates reactive oxygen species. A 2024 review concluded no health risks at up to 4% (PMID 40952777). Somewhat paradoxical: a sunscreen ingredient that can damage DNA under UV.

Part of the benzophenone family (Contact Allergen of the Year 2014). 57 reports of allergic contact dermatitis and 29 photoallergic reports in the literature (Hughes & Stone 2007). Less studied for endocrine effects than oxybenzone but shares the concerning structural class.

Degrades into benzophenone (suspected carcinogen and known endocrine disruptor) in a time- and temperature-dependent manner. Benzophenone detected in ALL octocrylene products tested (Lebaron 2021). Emerging photoallergen with cross-reactivity to ketoprofen (Avenel-Audran 2010). Environmentally persistent (0-10% removal in wastewater). Systemic absorption exceeds FDA threshold. Upgrading from caution to avoid based on the benzophenone degradation data.

Absorbed at 258x the FDA safety threshold (Matta 2019). Estrogenic and anti-androgenic activity in vitro and in vivo. Comprehensive HBM4EU review of 254 studies confirmed endocrine-disrupting properties at human-relevant concentrations (Krause 2023). Detected in breast milk and seminal fluid. Interferes with sperm calcium signalling. Potent coral toxicant. Banned in Hawaii, Key West, Palau, USVI, Aruba, parts of Mexico. The single most concerning chemical UV filter in widespread use.

Activates estrogen receptor alpha. Disrupts thyroid hormone axis: downregulates deiodinase 2, alters T3/T4 levels (Sharma 2022, Cocci 2022). Photodegrades via trans-to-cis isomerization, reducing UVB filtering efficacy. Accelerates photolysis of avobenzone when combined. Banned in Hawaii and Palau. No reason to choose it when safer alternatives exist.

The most potent estrogenic UV filter in the Schlumpf 2001 screening (ED50 309 mg/kg/day). Preferential ERbeta binding. Thyroid disruption: decreased serum T4, increased TSH. Delayed fetal ossification. Banned in all EU cosmetics effective May 2025 (Regulation 2024/996). Never FDA-approved. If you encounter this in a product, it is from a jurisdiction with weaker regulation.

Forms DNA photoproducts (thymine dimers) in cultured human cells under UV. Generates singlet oxygen and free radical intermediates. High rates of allergic contact dermatitis. Classified as Not GRASE (Category II) by FDA. Banned in EU and Canada. Voluntarily discontinued by virtually all manufacturers. Legacy ingredient.

PABA derivative. Absorbs UVB but the excited molecule reacts with DNA producing indirect damage similar to ionising radiation. Estrogenic activity in MCF-7 cells (Schlumpf 2001). Banned in EU and Canada. Still technically FDA Category III (approved up to 8%) but rarely used. If you see it on a label, the product is likely outdated.