🧬 Aging Wiki

bemotrizinol

Properties1
aliasesTinosorb S, BEMT, bis-ethylhexyloxyphenol methoxyphenyl triazine, anisotriazine, escalol S, BTEX

13 min read

Bemotrizinol (Tinosorb S, BEMT)

INCI: Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine IUPAC: 5-(2-ethylhexoxy)-2-[4-[4-(2-ethylhexoxy)-2-hydroxyphenyl]-6-(4-methoxyphenyl)-1,3,5-triazin-2-yl]phenol PubChem CID: 135487856 · CAS: 187393-00-6 (reported; see gap note above) · MW: 627.8 g/mol · Formula: C₃₈H₄₉N₃O₅ · InChIKey: XVAMCHGMPYWHNL-UHFFFAOYSA-N

Bemotrizinol (trade name Tinosorb S; abbreviated BEMT in the published literature) is an oil-soluble, broad-spectrum organic UV filter developed by DSM (now DSM-Firmenich). It absorbs across UVB (290–320 nm), UVA-II (320–340 nm), and UVA-I (340–400 nm), with a secondary absorption peak extending into the near-violet region. Bemotrizinol is also widely used as a photostabilizer for other UV filters — most importantly avobenzone (butyl methoxydibenzoylmethane) and ethylhexyl methoxycinnamate (octinoxate) — and is regarded by many formulators as the single most versatile organic broad-spectrum filter available.

Bemotrizinol is approved in the EU, UK, Australia/New Zealand, Canada, Japan, and many other jurisdictions but remains unapproved by the US FDA for OTC sunscreen use, stuck in the long-stalled Time and Extent Application (TEA) / OTC monograph backlog. Bemotrizinol is the explicit motivating example for the wiki’s R52 approved-ex-us convention (schema-history.md § R52): the “not FDA-approved” label in this case reflects US regulatory lag and the FDA drug-vs-cosmetic classification framework, not evidence weakness. The FDA has been in possession of the TEA since the early 2000s; by comparison, the EU authorized BEMT in 2000 (Annex VI entry 25) after full dossier review.

See uv-protection for the broad sunscreen intervention framework; this page is the atomic deep-dive on BEMT.

Structural note: s-triazine family

Bemotrizinol is built on a symmetrical 1,3,5-triazine (s-triazine) scaffold, which places it in the same chemical family as bisoctrizole (Tinosorb M, the water-dispersible micronized analog) and iscotrizinol (HDT) — all share the 2,4,6-triphenyl-triazine core. This family is structurally distinct from triasorb (PBT / phenylene bis-diphenyltriazine), which uses an asymmetric 1,2,4-triazine scaffold.

The two phenylphenol “arms” of BEMT each carry an ortho-hydroxyl group that forms an intramolecular hydrogen bond with the triazine nitrogen, locking the chromophore in a coplanar conformation. This molecular architecture enables both excellent UV absorption and very rapid excited-state deactivation (photon energy dissipated as heat via excited-state intramolecular proton transfer, ESIPT), which is the mechanistic basis of BEMT’s exceptional photostability 1.

Mechanism — broad-spectrum absorption and photostabilization

Primary mechanism: BEMT is a pure UVA + UVB absorber with dual absorption peaks:

  • UVB peak: ~310–315 nm
  • UVA-I/II peak: ~340 nm
  • Extended coverage: meaningful absorption to ~400 nm (extinction drops off in the near-visible; unlike mexoryl-400, BEMT does not provide significant 385–400 nm gap-filling)

When a UV photon is absorbed, the s-triazine chromophore undergoes ESIPT-facilitated excited-state deactivation, with near-quantitative return to ground state without photochemical degradation or significant fluorescence 1. This intrinsic photostability — unlike avobenzone, which photodegrades via trans→cis isomerization and Norrish rearrangements under UV exposure — is the fundamental property differentiating BEMT from most other organic filters.

Avobenzone photostabilization: Avobenzone photodegrades rapidly in isolation (losing ~25–60% of activity after typical UV exposure). BEMT prevents this degradation in a concentration-dependent manner via two proposed mechanisms: (1) UV-energy transfer / triplet-state quenching from avobenzone to BEMT, and (2) singlet-oxygen quenching. Chatelain and Gabard 2001 1 established this photostabilization role using thin-film irradiation experiments. This application is the primary commercial reason for BEMT’s global dominance in EU/AU/Canada premium sunscreen stacks — it “locks in” the UVA-I coverage of avobenzone over extended outdoor exposure, producing sustained broad-spectrum performance that SPF alone does not capture.

Octinoxate photostabilization: BEMT also reduces photodegradation of ethylhexyl methoxycinnamate (octinoxate/OMC) in combined formulations 1.

Result in finished formulas: BEMT-containing SPF 50+ formulations maintain their UVA protection ratio (PPD/UVA-PF) more stably through realistic use conditions than avobenzone-only formulations. The SPF number (UVB) may remain similar, but the practical UVA-PF is higher in BEMT stacks because the UVA filters don’t degrade as much.

Regulatory status

This table is the canonical reference; body text above documents the R52 framing.

RegionStatus
EUAuthorized since 2000; Annex VI entry 25 (Regulation EC No. 1223/2009) at ≤10% in rinse-off and leave-on cosmetic products. Safety reviewed by the SCCS (SCCS/1591/17, rev. 2018).
UK (post-Brexit MHRA/CTPA)Listed in UK Cosmetics Regulation Annex VI; ≤10%.
Australia (TGA)Listed ingredient permitted in listed/registered sunscreens; ≤10% aligns with EU.
Canada (Health Canada)Listed in Cosmetic Ingredient Hotlist (not prohibited); permitted in cosmetic sunscreens.
Japan (MHLW)Approved UV filter.
United States (FDA)Not GRASE. Not in 21 CFR §352 OTC monograph. A Time and Extent Application (TEA) was filed (DSM, ~2002) requesting inclusion; the FDA formally acknowledged the TEA but has not issued a Proposed Rulemaking. Modernizing access to newer sunscreen filters was a recurring theme in the 2019 Sunscreen Innovation Act era. Wang et al. 2026 2 and Turner & Torgerson 2025 3 document the ongoing FDA regulatory inertia and its public-health costs. As of April 2026, Wang et al. note FDA approval is “pending” — the regulatory path is the FDA’s new OTC Monograph Order Request (OMOR) process under the CARES Act.

Consequence for US-based users: sunscreens sold as OTC drug products in the US cannot contain BEMT. Import of foreign-market sunscreens for personal use is technically unregulated; commercially, products containing BEMT are unavailable in US retail drug/cosmetic channels but available via international import/pharmacy.

Photostability evidence

Bemotrizinol is one of the most photostable organic UV filters in commercial use. Key evidence:

StudyDesignKey result
Chatelain & Gabard 2001 1In-vitro thin-film irradiation (ISO 24444 era)BEMT itself shows minimal photodegradation after 20 MED; prevents avobenzone and OMC degradation in concentration-dependent manner; photostabilization complete at ~4% BEMT in formulation
Puglia 2014 4NLC nanocarrier formulation studyBEMT retains photostability when incorporated in nanostructured lipid carriers, unlike avobenzone and OMC
Du et al. 2026 5Quantum chemistry (TDDFT) + photodegradation assayAnomalous solvatochromism + rapid ESIPT relaxation synergistically inhibit BEMT photodegradation in polar media; ROS generation lower than less-stable organic filters

The practical consequence of BEMT photostability: SPF 50+ EU sunscreens containing BEMT + avobenzone typically achieve ISO UVA-PF ≥16 (the “broad-spectrum” threshold is critical wavelength ≥370 nm, PPD/SPF ratio ≥1/3) after UV exposure, whereas avobenzone formulations without BEMT lose a fraction of their UVA protection during use. gap/needs-replication — no published independent human-skin study has directly compared CPD or 8-OHdG accumulation in skin protected by BEMT-stabilized vs. non-stabilized avobenzone stacks over real-life use.

Human outcomes evidence

The evidence base for BEMT is unusual: the photostability and in-vitro efficacy data are excellent (multiple independent replications), but the translational gap to long-term photoaging outcomes is not closed by direct clinical trials.

Evidence typeSummary
SPF/UVA-PF testing (in vitro + in vivo ISO methods)BEMT enables SPF 50+ formulas that meet EU broad-spectrum criteria (PPD/SPF ≥ 1/3, critical wavelength ≥ 370 nm). This is regulatory-grade evidence for UV attenuation, not for photoaging reduction.
Photostabilizer role (Chatelain 2001 1)Prevents avobenzone degradation; established in vitro.
Pharmacokinetics (D’Ruiz 2023) 6MUsT + IVPT in volunteers using 6% BEMT sunscreen. Plasma BEMT concentrations rarely exceeded the FDA’s 0.5 ng/mL threshold. No systemic accumulation. Supports systemic safety for topical use.
Long-term photoaging RCTNone. No BEMT-specific RCT with photoaging histology (MMP-1, CPD count, collagen morphometry) as primary endpoint has been published. The inference that BEMT-stack sunscreens prevent photoaging better than US-approved stacks rests on bridging: (1) superior photostability → (2) more durable UVA protection → (3) less UVA-I-driven dermal damage. Each step is plausible but the chain has not been closed experimentally.

Relationship to the broader sunscreen RCT evidence: The Hughes 2013 trial 7 establishing that daily sunscreen use prevents photoaging used an Australian sunscreen formula (SPF 15–16, primarily chemical filters not including BEMT). The effect is attributed to the sunscreen-class intervention, not BEMT specifically. BEMT’s incremental contribution — specifically the photostabilization advantage — is not captured in that trial. For the general claim “sunscreen prevents photoaging,” the evidence is strong (see uv-protection); for the claim “BEMT-stack sunscreens prevent more photoaging than US-formulated stacks,” the evidence is limited.

gap/needs-head-to-head-us-vs-eu-stack · gap/no-biopsy-endpoint

Safety

  • SCCS review (SCCS/1591/17 rev. 2018): The Scientific Committee on Consumer Safety concluded BEMT is safe for use in leave-on and rinse-off cosmetic products at concentrations up to 10%. The dossier covered dermal absorption, genotoxicity, mutagenicity, sensitization (HRIPT), photo-sensitization, reproductive/developmental toxicity, and subchronic/chronic tox. Inhalation (spray) safety was not fully addressed; the EU authorization requires spray applications to be formulated to minimize inhalation risk. gap/needs-canonical-id for the SCCS opinion number (SCCS/1591/17 assigned based on secondary literature; verify against the full opinion PDF)
  • Pharmacokinetic safety (D’Ruiz 2023) 6: IVPT in reconstructed human epidermis + MUsT in human subjects using 6% BEMT SPF 50 sunscreen showed plasma concentrations rarely exceeding 0.5 ng/mL; no concerning accumulation after daily use.
  • Molecular weight barrier effect: MW 627.8 g/mol significantly exceeds the ~500 Da cutoff for efficient stratum corneum penetration; oil-solubility without surfactant enhancement further favours surface retention. Consistent with Puglia 2014 4 showing BEMT remains in stratum corneum in NLC formulations.
  • Adverse event reports:
    • Badaoui 2024 8 — a case report of allergic contact dermatitis (Type IV hypersensitivity) to BEMT in a sunscreen (first reported case in indexed English-language literature; designated “an emerging allergen?”). Represents the first independent dermatology case report of BEMT sensitization.
    • No photoallergy cases reported in indexed literature to date (as of June 2026).
  • Environmental: Fagervold et al. 2025 9 found BEMT was not biodegraded in marine sediment microcosm experiments after 100 days, consistent with other modern triazine filters. BEMT detected in Mediterranean seawater (Gandar 2025) 10. Unlike oxybenzone (direct coral bleaching mechanism), BEMT’s environmental aquatic toxicity is primarily persistence-based; no direct coral bleaching evidence has been published. Environmental-impact framing should not imply BEMT is “reef-safe” — it is simply uncharacterized for reef toxicity and confirmed to accumulate in marine sediment. gap/long-term-unknown (environmental fate)

BEMT vs. sibling UV filters

PropertyBEMT (Tinosorb S)Bisoctrizole (Tinosorb M)TriAsorB (PBT)Mexoryl 400 (MCE)
Scaffolds-triazine (oil-soluble)s-triazine (micronized aqueous dispersion)1,2,4-triazine (oil-soluble)Cyclohexenylidene cyanoacetate
MW627.8 Da659.0 Da540.6 Da322.4 Da
λmax (primary)~310–315 nm (UVB) + ~345 nm (UVA)~303 nm + ~360 nmBroadband UVB–HEV~385 nm (UVA-I)
CoverageUVB + UVA-II + UVA-IUVB + UVA-II + UVA-IUVB + UVA + HEV visible (400–450 nm)Ultra-long UVA-I gap-fill (380–400 nm)
Photostabilizer roleYes — photostabilizes avobenzone + OMCYes (also photostabilizes)No (needs no stabilizer itself)No avobenzone-stabilizer role published
EU authorization≤10%≤10%≤5%≤3%
FDA statusNot GRASE (TEA pending)Not GRASENot GRASENot GRASE
Independent adverse-event reports1 ACD case (Badaoui 2024)None indexedNone indexed1 ACD case (Loretan 2024, see mexoryl-400)
AvailabilityGlobal except USGlobal except USAvène-only (Pierre Fabre proprietary)La Roche-Posay UVMune line (L’Oréal proprietary)

BEMT is the workhorse broad-spectrum photostabilizer for EU/AU/CA market premium formulations. bisoctrizole covers the same spectral range as BEMT in aqueous formulations. triasorb adds HEV/visible-light coverage beyond what BEMT provides. mexoryl-400 fills a narrower gap (380–400 nm UVA-I) that BEMT only weakly covers.

Formulation context and product availability

BEMT is widely available in non-US market sunscreens. Common product lines include:

  • La Roche-Posay Anthelios line (most EU/AU SKUs containing BEMT) — typically paired with bisoctrizole, drometrizole trisiloxane (Mexoryl XL), or ecamsule (Mexoryl SX)
  • Neutrogena Ultra Sheer (EU formula) — BEMT + avobenzone
  • Bioré UV Aqua Rich (Japan) — BEMT + uvinul A plus + tinosorb M
  • Many European pharmacy-brand SPF 50+ sunscreens (Eucerin, Altruist, Bondi Sands EU line, etc.)

US formulations of the same brands (La Roche-Posay Anthelios Melt-In Milk SPF 60, Neutrogena Ultra Sheer US, etc.) do not contain BEMT — they use FDA-GRASE filters (avobenzone/homosalate/octisalate/octocrylene or ZnO/TiO₂).

Knowledge gaps and limitations

  • #gap/needs-canonical-id — CAS 187393-00-6 needs independent confirmation against PubChem synonyms list (API query at time of seeding did not return synonyms for CID 135487856); SCCS opinion number (SCCS/1591/17) needs confirmation against the full opinion document.
  • #gap/no-biopsy-endpoint — No published RCT with dermal biopsy (CPD, MMP-1 IHC, collagen morphometry) comparing BEMT-formulated sunscreens to US-formulated sunscreens on photoaging hard endpoints.
  • #gap/needs-head-to-head-us-vs-eu-stack — The specific contribution of BEMT’s photostabilization of avobenzone to net photoaging prevention (vs. matched-SPF US stack) has not been directly tested.
  • #gap/long-term-unknown — Environmental fate (aquatic bioaccumulation, coral/marine invertebrate toxicity) is uncharacterized beyond sediment-persistence evidence; “reef-safe” framing is unsupported.
  • #gap/needs-replication — Badaoui 2024 ACD case report is n=1; population-level sensitization rate unknown.

Cross-references

Footnotes

Footnotes

  1. doi:10.1562/0031-8655(2001)074<0401:pobmaa>2.0.co;2 · Chatelain E, Gabard B · Photochem Photobiol 2001;74(3):401–406 · in-vitro thin-film irradiation study · BEMT photostabilizes avobenzone and ethylhexyl methoxycinnamate in concentration-dependent manner; BEMT itself shows minimal photodegradation after 20 MED irradiation · COI: BASF/Ciba SC employees; founding photostabilization paper for BEMT · gap/no-fulltext-access ↩ ↩2 ↩3 ↩4 ↩5 ↩6

  2. doi:10.1016/j.jaad.2026.04.1970 · Wang SQ, Osterwalder U, Lim HW · J Am Acad Dermatol 2026 (ahead of print) · commentary / regulatory analysis · discusses pending FDA approval of bemotrizinol and potential impact on US sunscreen formulation · note: Osterwalder is a DSM employee; Wang/Lim are independent academic dermatologists ↩

  3. doi:10.1111/phpp.70032 · Turner CW, Torgerson L · Photodermatol Photoimmunol Photomed 2025;41:e70032 · commentary / regulatory analysis · FDA regulatory inertia for international UV filters (BEMT, bisoctrizole, ecamsule, drometrizole trisiloxane); >5 million US skin cancer diagnoses annually; OTC Monograph Order Request process as potential reform mechanism · COI: none disclosed ↩

  4. doi:10.1016/j.ejps.2013.09.023 · Puglia C, Damiani E, Offerta A, et al. · Eur J Pharm Sci 2014;51:211–217 · nanostructured lipid carrier (NLC) formulation study · BEMT, DHHB, and EHT retain photostability in NLC; avobenzone and OMC do not; skin penetration reduced when encapsulated · not a clinical outcomes study ↩ ↩2

  5. doi:10.1039/d6cp01207h · Du Y, Cao R, Ren J, Mu Y, He W · Phys Chem Chem Phys 2026 · TDDFT + photodegradation assay · anomalous solvatochromism + rapid ESIPT-facilitated excited-state relaxation underlie BEMT photostability in polar media; ROS generation suppressed · mechanistic explanation for BEMT photostabilization ↩

  6. doi:10.1016/j.yrtph.2023.105344 · D’Ruiz CD, Plautz JR, Schuetz R, Sanabria C, Hammonds J, Erato C, Klock J, Vollhardt J, Mesaros S · Regul Toxicol Pharmacol 2023;139:105344 · in-vitro permeation test (IVPT) + maximum-usage trial (MUsT) in volunteers · 6% BEMT sunscreen SPF 50; plasma BEMT rarely exceeded 0.5 ng/mL (FDA threshold); no systemic accumulation · clinical pharmacokinetic data submitted to FDA supporting TEA for BEMT OTC inclusion · COI: DSM (developer) ↩ ↩2

  7. doi:10.1016/j.annals.2013.09.024 · Hughes MCB, Williams GM, Baker P, Green AC · Ann Intern Med 2013;158:781–790 · RCT (903 adults, 4.5 yr) · daily vs. discretionary sunscreen use; daily use group had 24% less skin aging (photoaging score) · class-level RCT evidence; formula did not contain BEMT specifically — cited here to anchor the class-level inference that sustained broad-spectrum UV protection prevents photoaging ↩

  8. doi:10.1111/cod.14647 · Badaoui A · Contact Dermatitis 2024;91(5):443–445 · case report · n=1 · allergic contact dermatitis to BEMT (Tinosorb S) in a sunscreen; patch testing confirmed; designated “an emerging allergen?” · first indexed case report of BEMT contact sensitization in English literature ↩

  9. doi:10.1007/s11356-025-36772-y · Fagervold SK, Rohée C, Lebaron P · Environ Sci Pollut Res Int 2025;32:19823–19835 · marine sediment microcosm · BEMT not biodegraded after 100 days (along with most modern triazine filters); benzophenone-3, homosalate, octisalate degraded · environmental persistence finding ↩

  10. doi:10.1016/j.marpolbul.2025.117567 · Gandar A, Giraudo M, Perion T, et al. · Mar Pollut Bull 2025;212:117567 · targeted + untargeted screening in Mediterranean seawater · BEMT detected in coastal waters; octocrylene higher biodiversity risk score than BEMT · environmental detection study; not a toxicity/health study ↩

Graph View

Backlinks