Is Diacetyl safe in cosmetics?
Diacetyl has a safety rating of "POOR" in our database. EU status: prohibited. US status: permitted. 2 toxicological study endpoint(s) are available in our database.
Diacetyl
Also known as: Dimethyl glyoxal, Butanedione, 4-01-00-03644, BRN 0605398, EINECS 207-069-8 (+9 more)
INCI: DIACETYL
Diacetyl (CAS 431-03-8) is a cosmetic cosmetic ingredient functioning as Masking agent, fragrance ingredient. NOAEL 90 mg/kg bw/day (cross-referenced against ToxValDB ECHA IUCLID); EU Regulation 1223/2009 status: prohibited; GHS signal word DANGER. Industrial safety data is also available in the chemical safety database. Same-CAS public records also appear in industrial chemical safety and pharmaceutical data.
View industrial chemical safety profile for CAS 431-03-8 →
Auto-generated CPSR Part A draft with source citations
Cross-Vertical Regulatory Divergence
Diacetyl is prohibited in EU cosmetics but has active industrial GHS classifications (H225, H302, H315, H317, H318, H331, H373, H351).
Source: Cosmetics: ingredients.eu_status; Chemicals: ghs_classifications.signal_word/hazard_statement_code
Function
Masking agent, fragrance ingredient
Safety Rating
POOR
Chemistry & Identifiers
IUPAC Name
butane-2,3-dione
InChIKey
QSJXEFYPDANLFS-UHFFFAOYSA-N
Regulatory Status
EU EU Status
prohibited
US US Status
permitted
US Notes
Permitted as GRAS food flavoring (FEMA 2370); no specific FDA cosmetic prohibition
For full compliance data across multiple jurisdictions, use the Substance Compliance tool.
Safety Data
Margin of Safety, dermal absorption, and sensitization profile summaries for Diacetyl.
Calculate MoS for your specific formulation with the MoS Calculator.
Toxicological Studies
2 study endpoints found for Diacetyl. NOAEL (No Observed Adverse Effect Level) values are used to calculate the Margin of Safety per SCCS methodology.
| Endpoint | Value | Route | Species | Study Type | Source |
|---|---|---|---|---|---|
| NOAEL | 300 mg/kg bw/day | oral | rat | Special Toxicology Study | COSMOS_DB |
| NOAEL | 540 mg/kg bw/day | oral | rat | Subchronic | COSMOS_DB |
GHS Hazard Classification
Globally Harmonized System classification per ECHA C&L inventory and ILO/WHO International Chemical Safety Cards.
Signal Word
DANGER
Pictograms
FlamFlameSkullToxicCancerHealth haz
Hazard Statements
Highly flammable liquid and vapour Harmful if swallowed Toxic if inhaled Causes skin irritation Causes serious eye irritation Causes damage to respiratory system if inhaled Causes damage to respiratory system through prolonged or repeated exposure if inhaled Harmful to aquatic life
Short-term Exposure Effects
The substance is severely irritating to the eyes. The substance is irritating to the skin and respiratory tract. The substance may cause effects on the central nervous system, lungs and respiratory tract. Exposure at high levels could cause lowering of consciousness.
Long-term Exposure Effects
Lungs may be affected by repeated or prolongated exposure to the vapour. This may result in impaired functions. See Notes.
Routes of Exposure
The substance can be absorbed into the body by inhalation and by ingestion.
Pre-Calculated Safety Assessment
Pre-calculated NOAEL → SED → MoS audit trail for Diacetyl across SCCS product categories, with measured dermal absorption where available.
Sensitization AOP Dashboard
Adverse Outcome Pathway data across 5 assays (DPRA, KeratinoSens, hCLAT, LLNA, NESIL) aggregated from public sources.
DPRA Cys %
79%
DPRA Lys %
27%
KeratinoSens IC50
891.05 µM
hCLAT CV75
151.15 µg/mL
LLNA EC3
11.3%
NESIL
1350 µg/cm²
LLNA: Weak (1B)
GHS: 1B
Human: positive
Source: LLNA: Roberts et al. (1999); DPRA: Nukada et al. 2013 [DOI:10.1016/j.tiv.2012.11.006] | Bauch et al. 2012 [DOI:10.1016/j.yrtph.2012.05.013]; KS: Natsch et al. 2013 [DOI:10.1002/jat.2868] | Bauch et al. 2012 [DOI:10.1016/j.yrtph.2012.05.013]; hCLAT: Bauch et al. 2012 [DOI:10.1016/j.yrtph.2012.05.013] | Ashikaga et al. 2010 [DOI:10.1177/026119291003800403]; HPPT: [88] Epstein WL (1976): Report to RIFM, 8 October, unpublished.
HRIPT Human Patch Test Studies
1 human repeat insult patch test aggregated from dermatological literature.
| Test Type | N | Sensitized | Dose µg/cm² | NESIL µg/cm² | Potency |
|---|---|---|---|---|---|
| HMT | - | 0 | 1350 | - | - |
ECHA REACH Registration
European Chemicals Agency REACH dossier and Substances of Very High Concern listing.
Registration Type
Intermediate
Tonnage Band
Intermediate use only
Substance Type
SUBSTANCE
SVHC Candidate
No
Additional Ingredient Properties
1 property record from structured ingredient metadata.
fermentation
{"cas_number": "varies", "ingredient_class": "microbial_metabolite", "production_organism": "bacteria", "fermentation_type": "aerobic", "substrate_feedstock": "glucose, amino acids", "bioactive_compounds_produced": "Diacetyl", "mechanism_of_action_skin": "cell signaling, antimicrobial, antioxidant, metabolic regulation", "skin_benefit_primary": "antioxidant", "skin_benefit_secondary": "anti_inflam…
PubChem Annotations
Safety and regulatory annotations from PubChem (NCBI) aggregated sources.
Safety (5)
Carcinogen Classification
No indication of carcinogenicity (not listed by IARC). (L135)
Source: Toxin and Toxin Target Database (T3DB)
Carcinogen Classification
2,3-Butanedione | TR-593: Toxicology and Carcinogenesis Studies of 2,3-Butanedione (CASRN 431-03-8) in Wistar Han [Crl:WI (Han)] Rats and B6C3F1/N Mice (Inhalation Studies) (2018 ) | 07/13/17 | Some Evidence | Some Evidence | No Evidence | Equivocal Evidence | Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenic activity of 2,3-butanedione in ma
Source: NTP Technical Reports
Evidence for Carcinogenicity
A4: Not classifiable as a human carcinogen.
Source: Hazardous Substances Data Bank (HSDB)
ICSC Safety Card
1168
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Skin Eye Respiratory Irritation
A skin irritant.
Source: Hazardous Substances Data Bank (HSDB)
Regulatory (2)
JECFA Number
408
Source: Joint FAO/WHO Expert Committee on Food Additives (JECFA)
JECFA Evaluation
DIMETHYLDIKETONE | 1998 | No safety concern at current levels of intake when used as a flavouring agent | TRS 891-JECFA 51/103 | FAS 42-JECFA 51/353
Source: Joint FAO/WHO Expert Committee on Food Additives (JECFA)
Function Categories & List Membership
Cosmetic/Chemical Function Categories
Flavouring and nutrient
Fragrance
Regulatory List Membership (2)
IFRA Fragrance Transparency List
FDA Substances Added to Food (EAFUS)
Expert Verdict
Expert safety assessment and concern-level summary for Diacetyl.
Regulatory Flags
fragrance-component
ifra_fragrance
fda_food_additive
jecfa_safe
NOAEL Studies Summary
View details ->Public NOAEL study rows linked to Diacetyl by CAS number or substance name.
Studies
2
Lowest NOAEL
300 mg/kg bw/day
Highest NOAEL
540 mg/kg bw/day
COSMOS_DB
Known Synonyms
Dimethyl glyoxal
Butanedione
4-01-00-03644
BRN 0605398
EINECS 207-069-8
FEMA No. 2370
Glyoxal, dimethyl-
UNII-K324J5K4HM
2,3-butandione
Acetoacetaldehyde
Butadione
Butan-2,3-dione
Butane-2,3-dione
Butanedione [UN2346]
Chemical Function
Fragrance
Flavouring and nutrient
Regulatory Lists
animal_products
IFRA Transparency
Europe
food_additive; Substances Added to Food (formerly EAFUS) (2/2019)
Australian Status
AICIS status: listed
Cross-Vertical Safety Context
Same-CAS public records found in pharmaceutical data.
SOURCE
ChEMBL / DrugCentral / FAERS
DB_PHARMA CAS match
Pharmaceutical Data
Same-CAS rows from the pharmaceutical spoke database.
Compound
BUTANEDIONE
ChEMBL ID
CHEMBL365809
Frequently Asked Questions
Is Diacetyl allowed in the EU?
Diacetyl EU regulatory status: prohibited. This is based on EU Regulation 1223/2009 and its amendments.
What does Diacetyl do in cosmetics?
Diacetyl functions as: Masking agent, fragrance ingredient. It is classified as a cosmetic ingredient in our database. CAS number: 431-03-8.
What is the NOAEL for Diacetyl?
The NOAEL (No Observed Adverse Effect Level) for Diacetyl is 300 mg/kg bw/day based on a Special Toxicology Study study via oral route in rat. A total of 2 study endpoints are available. Source: COSMOS_DB.
Is Diacetyl classified as hazardous under GHS?
Diacetyl carries a GHS signal word of "DANGER". Hazard statements: Highly flammable liquid and vapour Harmful if swallowed Toxic if inhaled Causes skin irritation Causes serious eye irritation Causes damage to respiratory system if inhaled Causes damage to respiratory system through prolonged or repeated exposure if inhaled Harmful to aquatic life. This classification is based on the ILO/WHO International Chemical Safety Card and ECHA C&L inventory data. Note: GHS classification applies to the pure substance — at cosmetic use concentrations, hazard thresholds may not be met.
Is Diacetyl used outside cosmetics?
Diacetyl also appears in industrial chemical safety and pharmaceutical data. The cross-vertical cards on this page render same-CAS public rows from the matched databases.
Does Diacetyl have different safety status in cosmetics vs industrial chemicals?
Diacetyl is prohibited in EU cosmetics but has active industrial GHS classifications (H225, H302, H315, H317, H318, H331, H373, H351).
Compliance Tools
Check Diacetyl compliance across multiple jurisdictions:
Ingredient Decoder
Paste a full ingredient list for instant analysis
82 Allergen Checker
Check for EU declarable fragrance allergens
Substance Compliance
Check compliance across multiple jurisdictions
MoS Calculator
Calculate Margin of Safety using SCCS methodology
Heavy Metal Limits
Compare limits across jurisdictions
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