🧬 Aging Wiki

bisoctrizole

Properties1
aliasesTinosorb M, MBBT, methylene bis-benzotriazolyl tetramethylbutylphenol

15 min read

Bisoctrizole (Tinosorb M, MBBT)

INCI: METHYLENE BIS-BENZOTRIAZOLYL TETRAMETHYLBUTYLPHENOL USAN: Bisoctrizole · CAS: 103597-45-1 · EC: 403-800-1 · PubChem CID: 3571576 · ChEMBL: CHEMBL2104957 MW: 658.9 g/mol · Formula: C₄₁H₅₀N₆O₂ · InChIKey: FQUNFJULCYSSOP-UHFFFAOYSA-N

Bisoctrizole (trade name Tinosorb M; also Tinuvin 360, UV-360) is a broad-spectrum topical UV filter supplied as an aqueous microfine-particle dispersion of organic microparticles. It is the canonical hybrid UV filter: it both absorbs UV photons (via the benzotriazole chromophore) and physically scatters UV via its particulate physical state, distinguishing it from purely molecular organic absorbers (avobenzone, ecamsule, bemotrizinol) and from purely physical inorganic scatterers (ZnO, TiO₂). It is approved in the EU, UK, Australia, Canada, Japan, and many other jurisdictions. It is not FDA-approved for OTC sunscreen use in the United States (regulatory lag — see §Regulatory status).

Bisoctrizole is the structural model for this wiki’s sibling UV-filter pages. Compare with triasorb (TriAsorB/PBT — similarly hybrid, but triazine-scaffold, HEV reflectance) and mexoryl-400 (MCE — pure molecular absorber targeting 380–400 nm UVA-I tail). See uv-protection for the broader photoprotection intervention framework.

Mechanism — hybrid absorber + scatterer

Bisoctrizole’s dual mechanism reflects its unique physical state. Unlike conventional organic UV filters, which are dissolved in the formulation’s oil phase, bisoctrizole is processed as microfine solid particles (primary particle diameter approximately 100–200 nm; aggregates ~200 nm in aqueous dispersion) suspended in water.

Absorption arm

The active chromophore is the 2-(2-hydroxyphenyl)benzotriazole (HPBT) moiety — a well-established UV absorber class. Bisoctrizole carries two such benzotriazolyl groups connected via a methylene bridge through two hindered phenol units. The excited-state deactivation mechanism is intramolecular proton transfer (ESIPT) combined with excited-state tautomerism. Upon UV absorption, the enol form undergoes excited-singlet-state proton transfer to the benzotriazole nitrogen, generating a keto tautomer that undergoes fast internal conversion back to the ground state, dissipating photon energy as heat without re-emission or photoproduct formation 1. In aqueous dispersion, the particles form π-stacked dimers, producing a bathochromic shift in UV absorption compared with dilute organic solvent — this extends effective coverage toward the longer UVA-I end of the spectrum.

Spectral coverage: UVB (290–320 nm) + UVA-II (320–340 nm) + UVA-I (340–400 nm). The absorption is broad rather than peak-specific — no single sharp λmax defines performance. The particle state creates effective absorption across the entire biologically active UV range.

Scattering arm

In its microfine-particle form, bisoctrizole additionally scatters UV photons via Mie scattering (particle diameter in the range where both forward and back-scattering are significant). This physical-scatter component is absent in dissolved organic filters and provides:

  • Additional attenuation of UV photons that reach the particle surface but are not absorbed
  • An attenuation profile that continues somewhat into the near-visible range (unlike purely molecular absorbers that drop sharply at the long-UV edge)

The combination means bisoctrizole behaves as a broad-spectrum attenuator rather than as a wavelength-specific absorber, giving it inherent “critical wavelength” values that typically exceed the 370 nm EU broad-spectrum threshold 2.

Photostability

Photostability is bisoctrizole’s key clinical advantage. ESIPT-mediated deactivation returns the chromophore to its exact ground-state structure — there is no photo-isomerization, no photobleaching, and no formation of photodegraded products at typical formulation concentrations. In combination studies, bisoctrizole substantially reduces the photodegradation of photolabile co-filters (especially avobenzone), acting as a photostabilizer for the overall formula stack 2. This is mechanistically distinct from the co-photostabilizer role of octocrylene (which quenches avobenzone’s excited triplet state by energy transfer); bisoctrizole’s photostabilization effect likely involves physical energy absorption + quenching that reduces the photon flux available to degrade co-filters.

Regulatory status

RegionStatusConcentration limit
EUListed in Annex VI (entry 28) of Regulation (EC) 1223/2009. SCCS opinion SCCS/1469/12 (2012) concluded safe up to 10%. Applies to all EU member states.≤10% (both rinse-off and leave-on)
United KingdomRetained in UK cosmetics regulation post-Brexit; same limit.≤10%
Australia (TGA)Listed sunscreen ingredient; permitted in therapeutic-goods sunscreens.≤10%
Canada (Health Canada)Listed in Health Canada’s Cosmetic Ingredient Hotlist as permitted; usable in non-drug cosmetic sunscreens. Also approvable under the sunscreen monograph, unlike TriAsorB.≤10%
Japan / South Korea / BrazilPermitted in cosmetic sunscreen formulations (exact limits vary by jurisdiction but ≤10% is common).≤10%
United States (FDA)Not GRASE. Bisoctrizole was the subject of an old-pathway request under the 1996 FDAMA “Time and Extent Application” (TEA) framework (submitted by BASF); the FDA published a proposed rule in 2019 that classified bisoctrizole as Category III (insufficient safety data to determine GRASE status, pending additional studies). Products containing bisoctrizole cannot be sold as US sunscreens. The FDA’s new Over-the-Counter Monograph Order Request (OMOR) process may eventually provide a path to approval — Turner 2025 argues this is a critical public health priority 3.—

US regulatory context. FDA Category III does not mean unsafe — it means safety data under FDA’s current standards (including dermal absorption pharmacokinetics equivalent to the Matta 2019/2020 protocol) have not been formally submitted or reviewed under the new framework. The EU SCCS opinion found bisoctrizole safe at ≤10% based on a comprehensive dossier including reproductive and genetic toxicity; the US gap reflects a classification and process issue rather than a safety signal 3.

Particle-size characterization and nanomaterial status

Bisoctrizole in commercial formulations (e.g., Tinosorb M aqueous dispersion 50%) has a primary particle diameter reported in the 100–200 nm range by the manufacturer (BASF). EU nanomaterial regulations (Commission Regulation 2022/692) define nanomaterials as particles with ≥50% of particles in the 1–100 nm range by number distribution. Whether commercial bisoctrizole dispersions meet this definition depends on the particle-size distribution measurement method and instrument; BASF has reported that the aggregate/agglomerate size exceeds 100 nm and the particles are insoluble — placing the product in a regulatory grey zone that is ongoing. The EU has not explicitly designated Tinosorb M as a nanomaterial-regulated substance under cosmetics nanomaterial rules as of 2026. SCCS/1469/12 did evaluate the nano/particle question and concluded the particulate form was safe at ≤10%.

Practical implication for mechanism: the particulate physical state is essential for the scatter contribution to bisoctrizole’s efficacy. Formulators who dissolve bisoctrizole in organic solvents destroy the scattering arm and may reduce its photostability function as a co-filter stabilizer. Commercially, bisoctrizole is always used in its aqueous dispersion form.

Dermal absorption and systemic exposure

Bisoctrizole’s particle form and high molecular weight (658.9 Da) strongly limit transdermal penetration. Mavon et al. 2007 quantified this directly using in vitro Franz cells with human excised skin and in vivo tape-strip recovery 4:

  • 90% of applied MBBT was recovered in the first 15 tape strips (upper stratum corneum)

  • < 0.1% detected in the receptor fluid after 24 h
  • No detectable MBBT in viable epidermis or dermis layers

The combination of high MW, solid-particle physical state, and hydrophilicity (the aqueous dispersion formulation) effectively restricts bisoctrizole to the stratum corneum. This is a material safety distinction from most conventional chemical filters. The Matta 2019/2020 FDA maximal-use PK protocol has not been applied to bisoctrizole (since it is not under US jurisdiction), but based on physicochemistry, plasma levels under normal use are expected to be negligible.

Endocrine activity. Bisoctrizole shows no detectable estrogenic, androgenic, or thyroid-disrupting activity in standard in vitro screening assays (including yeast-based estrogenicity, H295R steroidogenesis). This contrasts with legacy filters like oxybenzone and octinoxate. No endocrine concern was identified in the SCCS/1469/12 review. A 2017 Korean risk assessment confirmed absence of estrogenic activity at concentrations relevant to cosmetic use 5.

Human evidence — photoprotection efficacy

There are no published RCTs specifically evaluating bisoctrizole’s contribution to photoaging endpoints (CPD, 8-OHdG, MMP-1 induction, clinical photoaging scoring) in isolation. The human evidence for bisoctrizole is limited to:

  1. SPF and critical wavelength — in vitro and in vivo: Bisoctrizole-containing formulas consistently exceed the EU broad-spectrum “critical wavelength ≥370 nm” threshold. SPF contributions from bisoctrizole at ≤10% in finished sunscreens have been validated in multiple published formulation studies, confirming its efficacy contribution to the UV-attenuating stack 6 2.

  2. Photostabilization of co-filters: Gaspar & Maia Campos 2006 demonstrated that adding bisoctrizole to a formula containing avobenzone (photolabile) substantially improved the photostability of the combination 2. This is a well-replicated formulation finding and the basis for bisoctrizole’s common role as a “photostabilizer” in EU sunscreen stacks.

  3. Regulatory evidence base: The SCCS/1469/12 dossier reviewed safety data but the dossier’s efficacy section is not a primary research paper per se. EU Annex VI listing confirms regulatory acceptance of efficacy at ≤10%.

  4. Turner 2025 review: Describes bisoctrizole alongside bemotrizinol and drometrizole trisiloxane as offering “broader and more stable UV protection” than currently FDA-available US filters — this is a secondary characterization, not a primary clinical efficacy trial 3.

What is absent: No published intra-individual hemiface or hemibody RCT isolating bisoctrizole’s contribution to photoaging endpoints. No head-to-head data comparing bisoctrizole to an equivalent-SPF formula without bisoctrizole on hard endpoints (CPD quantification, 8-OHdG, MMP-1 IHC, wrinkle-depth profilometry). Efficacy is inferred from spectroscopy + photostability data and the proven pharmacology of UV attenuation → reduced photodamage (mechanistically validated in the Fisher 1996 and Hughes 2013 literature), not from bisoctrizole-specific outcome trials.

gap/no-direct-comparator-rct · gap/no-biopsy-endpoint

Safety — adverse reactions

Bisoctrizole has a strong safety profile by dermatological standards for a widely used UV filter but has documented contact sensitization potential:

  • Allergic contact dermatitis (Type IV): At least three published case-series/reports document positive patch or photopatch test reactions to MBBT 7 8 9. In most cases, the relevant allergen in Tinosorb M-based commercial formulas is decyl glucoside (a non-ionic surfactant used in the dispersion) rather than bisoctrizole itself 10 11 — bisoctrizole-specific sensitization is documented but considerably rarer than decyl-glucoside sensitization. When patch testing a patient who reacts to a Tinosorb M-containing product, both components should be tested separately.

  • Photoallergic contact dermatitis: Rare — the photopatch-positive cases in Gonzalez 2011 (two patients with atopic + chronic actinic dermatitis) suggest photosensitivity in susceptible populations. Population-level photopatch data from Codeço 2023 (12-year experience, 223 patients) characterizes the “newer UV filters” (including MBBT) as showing only “low reactivity” in aggregate 12. The absolute sensitization rate in the general population is very low.

  • Reproductive/systemic toxicity: No reproductive, carcinogenic, or systemic endocrine concerns were identified in the SCCS/1469/12 review. Kim 2026 Korean safety assessment (most recent dedicated safety paper) funded by the Korean MFDS corroborates the SCCS safety conclusions 13.

  • Ecotoxicity: Multiple studies confirm bisoctrizole (MBBT) is environmentally persistent. Fagervold 2025 14 showed it was not biodegraded in marine sediment microcosms after 100 days. Fagervold 2022 (wastewater-treatment sludge enrichment) confirmed resistance to biodegradation even after 120 days 15. Thorel 2020 evaluated 10 UV filters in Artemia salina and Tetraselmis sp. — bisoctrizole was among the more eco-compatible filters (lower ecotoxicity than oxybenzone, octocrylene, homosalate), but its environmental persistence means it accumulates in sediments regardless 16. gap/long-term-unknown for sediment ecological impact.

Bisoctrizole vs sibling UV filters

PropertyBisoctrizole (MBBT)TriAsorB (PBT)Mexoryl 400 (MCE)
MW658.9 g/mol540.6 g/mol322.4 g/mol
Physical stateAqueous microfine-particle dispersion (hybrid)Organic particulate (oil-dispersible)Molecular — fully dissolved
Primary mechanismAbsorption (benzotriazole ESIPT) + Mie scatterAbsorption + HEV reflectanceMolecular absorption
Spectral peakBroad UVB–UVA-I; no sharp λmaxUVB–UVA + HEV 400–450 nmλmax ~385 nm (UVA-I tail)
EU max concentration10%5%3%
Photostabilizer role?Yes — stabilizes avobenzoneNo separate dataNo
US FDA statusNot GRASE (Category III)Not GRASENot GRASE
CanadaPermittedNot on Sunscreen MonographPermitted
HEV coverage without pigmentsNoYes (reflectance mechanism)No
Contact sensitization concernYes (rare MBBT + decyl glucoside vehicle)None published1 case report (MCE direct)
Environmental persistenceHigh (not biodegraded in sediments)High (same finding)Not separately tested

When to prefer bisoctrizole: broad-spectrum coverage including UVB + full UVA with a single ingredient; formulas where photostabilization of avobenzone or other labile filters is desired; the higher 10% EU limit allows greater efficacy headroom. The 10% ceiling vs 5% for TriAsorB means bisoctrizole can be used at twice the concentration, which matters for achieving high SPF + high UVA-PF simultaneously.

Positioning relative to the stack: In the most protective EU-available sunscreens, bisoctrizole is commonly combined with bemotrizinol (Tinosorb S — broad-spectrum molecular absorber), ecamsule (Mexoryl SX — UVA-II absorber), and sometimes drometrizole trisiloxane (Mexoryl XL — UVA + UVB absorber). See bemotrizinol, ecamsule, drometrizole-trisiloxane for individual pages.

Product availability

Bisoctrizole (Tinosorb M) is manufactured by BASF SE and is available to licensed cosmetic formulators worldwide outside the US. It appears in sunscreens across multiple brands in EU, UK, Australia, and Canada. Notable high-SPF European formulations routinely include MBBT at 5–10%. US-market consumers must source non-US formulations (often via grey-market import) to access it.

Limitations and gaps

  • No isolated efficacy RCT: all clinical photoprotection evidence uses completed formulas; bisoctrizole’s isolated contribution to CPD reduction or other hard photoaging endpoints has never been measured in a controlled design. gap/no-direct-comparator-rct
  • Nanomaterial regulatory uncertainty: the EU nanomaterial classification is unresolved and may affect labelling/registration requirements. gap/needs-canonical-id (for the nano/particle-size characterization)
  • Ecotoxicology long-term: sediment accumulation trajectory over multi-decade environmental exposure is unknown. gap/long-term-unknown
  • Decyl glucoside co-sensitization: most published allergy cases reflect vehicle-formula sensitization rather than MBBT-specific sensitization; the true MBBT-specific sensitization rate is undercharacterized.
  • US regulatory pathway: FDA’s OMOR process is slow; no approval timeline is available. gap/long-term-unknown

Cross-references

  • uv-protection — parent intervention page (UV-filter mechanisms + evidence framework; bisoctrizole sits in § Chemical filters)
  • triasorb — sibling hybrid organic-particulate filter (Pierre Fabre / Avène; HEV reflectance)
  • mexoryl-400 — sibling ultra-long UVA-I absorber (L’Oréal)
  • bemotrizinol — broad-spectrum molecular absorber commonly co-formuled with bisoctrizole (Tinosorb S) [implicit stub]
  • ecamsule — UVA-II molecular absorber (Mexoryl SX) [implicit stub]
  • drometrizole-trisiloxane — UVA+UVB molecular absorber (Mexoryl XL) [implicit stub]
  • iscotrizinol — UVA organic filter [implicit stub]
  • tinosorb-a2b — another BASF UV filter [implicit stub]
  • skin-aging — primary photoaging endpoint
  • genomic-instability — UV-induced CPD/6-4PP/8-OHdG DNA damage burden
  • loss-of-proteostasis — MMP-driven dermal collagen/elastin degradation
  • chronic-inflammation — UV-NF-κB cytokine induction

Footnotes

Footnotes

  1. doi:10.1021/acs.jpca.9b08820 · Naumov S, Herzog B, Abel B · J Phys Chem A 2020;124(5):859–869 · spectroscopic + computational · MBBT aqueous dispersion; excited-state deactivation via intramolecular ESIPT tautomerism + fast internal conversion; π-stacked dimers cause bathochromic shift vs organic solvent; foundational photophysics paper for bisoctrizole deactivation mechanism · COI: BASF (Herzog) co-authored · gap/needs-canonical-id — DOI unconfirmable via Crossref, PubMed, or ACS public endpoint at 2026-06-09; paper title/content is plausible but cannot be verified without paywalled access ↩

  2. doi:10.1016/j.ijpharm.2005.08.029 · Gaspar LR, Maia Campos PMBG · Int J Pharm 2006;307(2):123–128 · in-vitro photostability evaluation · formulation study · bisoctrizole co-formulated with avobenzone substantially improved photostability vs avobenzone alone; MBBT photostable across repeat UV exposures · independent (non-BASF) photostability data ↩ ↩2 ↩3 ↩4

  3. doi:10.1111/phpp.70032 · Turner CW, Torgerson L · Photodermatol Photoimmunol Photomed 2025;41(5):e70032 · review · bisoctrizole, bemotrizinol, drometrizole trisiloxane, and ecamsule described as offering “broader and more stable UV protection” vs currently FDA-approved US filters; OMOR pathway as potential route to US approval; strong public health framing · COI: none declared; authors are US dermatologists ↩ ↩2 ↩3

  4. doi:10.1159/000096167 · Mavon A, Miquel C, Lejeune O, Payre B, Moretto P · Skin Pharmacol Physiol 2007;20(1):10–20 · in-vitro Franz cell + in-vivo tape-strip · n=6 volunteers in-vivo; excised human skin in-vitro · > 90% MBBT recovered in first 15 tape strips; < 0.1% in receptor fluid at 24 h; no viable-epidermis penetration · COI: BASF-affiliated institution · primary dermal-penetration reference ↩

  5. doi:10.1016/j.toxlet.2017.07.294 · Lim S-K, Kim M-K, Suh H-S, Kim M-H, Baek S-H, Lee B-M · Toxicol Lett 2017;280 Suppl 1:S240 (conference proceedings) · risk assessment · MBBT; no estrogenic activity at cosmetic-use concentrations; Korean MFDS-sponsored risk assessment · abstract-level; full paper details not confirmed ↩

  6. doi:10.1111/jocd.14779 · Ruscinc N, Morocho-Jácome AL, Martinez RM, et al. (9 authors) · J Cosmet Dermatol 2022;21(10):4765–4774 · in-vitro SPF + in-vivo SPF + photostability · formulation study · bisoctrizole-containing sunscreen was photostable; Vaccinium myrtillus extract co-formulation reduced SPF, emphasising need for per-formula testing · no MBBT-isolated efficacy arm ↩

  7. doi:10.2310/6620.2011.10095 · Gonzalez ME, Soter NA, Cohen DE · Dermatitis 2011;22(2):106–111 · case report · n=2 (atopic dermatitis + chronic actinic dermatitis) · positive patch and photopatch test reactions to MBBT; documents both contact and photoallergic sensitization potential in susceptible patients · first published MBBT photosensitivity case series ↩

  8. doi:10.1111/cod.12417 · Liuti F, Borrego L · Contact Dermatitis 2015;73(3):192–193 · case report · n=1 · contact dermatitis traced to Tinosorb M; advocates patch testing with pure MBBT (not only the commercial dispersion) to distinguish MBBT vs vehicle sensitization · PMID 26264779 ↩

  9. doi:10.1111/j.1600-0536.2007.00961.x · González-Pérez R, Ratón-Nieto JA, et al. · Contact Dermatitis 2007;57(6):390–392 · case series · n=4 · allergic contact dermatitis to Tinosorb M; one of the earliest published series; 26 citations ↩

  10. doi:10.1097/DER.0000000000000267 · Loranger C, Alfalah M, Ferrier Le Bouedec MC, Sasseville D · Dermatitis 2017;28(1):3–13 · review · decyl glucoside (non-ionic surfactant used in Tinosorb M dispersion) as a hidden allergen; most Tinosorb M-attributed allergy cases likely reflect decyl-glucoside sensitization · key caveat for interpreting sensitization data ↩

  11. doi:10.1111/cod.13470 · Monteiro AF, Paulino M, Máquina A, Amaro C, Viana I · Contact Dermatitis 2020;83(4):317–319 · case series · n=3 · decyl glucoside as persistent allergen in Tinosorb M; advocates separate patch testing of MBBT active and decyl glucoside vehicle ↩

  12. doi:10.1111/cod.14536 · Codeço C, Alves PB, Figueiredo AC, Flor D, Gonçalo M · Contact Dermatitis 2023;88(5):373–381 · retrospective photopatch series · n=223 patients over 12 years · newer UV filters including MBBT showed “low reactivity” in aggregate photopatch testing; ketoprofen and topical NSAIDs were the main culprits · COI: none declared · independent population-level photopatch context ↩

  13. doi:10.1007/s43188-026-00350-2 · Kim M, Kim SB, Lee JD, Yoon T, Kim K-B, Kwack SJ, Lee JY · Toxicol Res 2026 (epub May 2026) · safety assessment · Korean MFDS-funded comprehensive safety assessment of MBBT; corroborates SCCS conclusions · gap/no-fulltext-access — abstract-level; full PDF not confirmed ↩

  14. doi:10.1007/s11356-025-36772-y · Fagervold SK, Rohée C, Lebaron P · Environ Sci Pollut Res Int 2025;32(33):19823–19835 · marine sediment microcosms · MBBT not biodegraded after 100 d; only benzophenone-3, homosalate, and ethylhexyl salicylate were degraded · environmental persistence finding ↩

  15. doi:10.1016/j.scitotenv.2021.151806 · Fagervold SK, Lebaron P · Sci Total Environ 2022;820:151806 · WWTP sludge enrichment culture · MBBT did not degrade even after 120 days; same finding in wastewater-treatment context ↩

  16. doi:10.3390/toxics8020036 · Thorel E, Clergeaud F, Jaugeon L, Rodrigues AMS, Lucas J, Stien D, Lebaron P · Toxics 2020;8(2):36 · ecotoxicology (marine microalgae + brine shrimp) · MBBT among more eco-compatible filters vs oxybenzone/octocrylene/homosalate; nonetheless not classified as ecologically inert given persistence data ↩

Graph View

Backlinks