Is Hydroquinone safe in cosmetics?
Hydroquinone has a safety rating of "POOR" in our database. EU status: prohibited. US status: restricted. 10 toxicological study endpoint(s) are available in our database.
Hydroquinone
Also known as: 1,4-Benzenediol, Dihydroxybenzene, Benzene, p-dihydroxy-, Black and White Bleaching Cream, Derma-Blanch (+14 more)
INCI: HYDROQUINONE
Hydroquinone (CAS 123-31-9) is a cosmetic active ingredient functioning as Tyrosinase inhibitor; competitive inhibitor and cytotoxic agent to melanocytes;. NOAEL 20 mg/kg bw/day (cross-referenced against ToxValDB ECHA IUCLID); EU Regulation 1223/2009 status: prohibited. 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 123-31-9 →
Auto-generated CPSR Part A draft with source citations
Cross-Vertical Regulatory Divergence
Hydroquinone is prohibited in EU cosmetics but has active industrial GHS classifications (H302, H312, H317, H318, H341, H351, H400, H410).
Source: Cosmetics: ingredients.eu status; Chemicals: ghs classifications.signal word/hazard statement code
Function
Tyrosinase inhibitor; competitive inhibitor and cytotoxic agent to melanocytes; inhibits both melanin synthesis and DNA synthesis in melanocytes; benchmark for all modern depigmenting actives
Safety Rating
POOR
Regulatory Status
EU EU Status
prohibited
US US Status
restricted
US Notes
Reclassified from OTC to prescription-only under MoCRA/CARES Act 2020. FDA has not issued final Rx rule; interim: OTC products without NDA receive warning letters. CIR concluded safe at ≤1% in rinse-off only. Rx 4% available under physician supervision. Saudi Arabia 2025 study found HQ in 80% of unregulated skin-lightening samples despite prescription restrictions. Banned or Rx-only in Japan, Australia, New Zealand, and multiple African and Asian markets.
For full compliance data across multiple jurisdictions, use the Substance Compliance tool.
Safety Data
Margin of Safety, dermal absorption, and sensitization profile summaries for Hydroquinone.
Calculate MoS for your specific formulation with the MoS Calculator.
Toxicological Studies
10 study endpoints found for Hydroquinone. 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 | =3840 mg/kg | dermal | rat | general toxicity | CIR Safety Assessment |
| NOAEL | =3840 mg/kg | dermal | rat | general toxicity | CIR Safety Assessment |
| NOAEL | =3840 mg/kg | dermal | rat | general toxicity | CIR Safety Assessment |
| NOAEL | =3840 mg/kg | dermal | rat | general toxicity | CIR Safety Assessment |
| NOAEL | =4800 mg/kg | dermal | mouse | general toxicity | CIR Safety Assessment |
| NOAEL | =4800 mg/kg | dermal | mouse | general toxicity | CIR Safety Assessment |
| NOAEL | =4800 mg/kg | dermal | mouse | general toxicity | CIR Safety Assessment |
| NOAEL | =4800 mg/kg | dermal | mouse | general toxicity | CIR Safety Assessment |
| NOAEL | =73.9 mg/kg bw/day | dermal | Rat | subchronic | ECHA |
| NOAEL | =109.6 mg/kg bw/day | dermal | Rat | subchronic | ECHA |
GHS Hazard Classification
Globally Harmonized System classification per ECHA C&L inventory and ILO/WHO International Chemical Safety Cards.
Short-term Exposure Effects
The substance is severely irritating to the eyes. The substance is irritating to the skin and respiratory tract.
Long-term Exposure Effects
Repeated or prolonged contact with skin may cause dermatitis. Repeated or prolonged contact may cause skin sensitization. The substance may have effects on the eyes and skin. This may result in discolouration of the conjunctiva and cornea and skin depigmentation. This substance is possibly carcinogenic to humans.
Routes of Exposure
The substance can be absorbed into the body by inhalation, through the skin and by ingestion.
Pre-Calculated Safety Assessment
Pre-calculated NOAEL → SED → MoS audit trail for Hydroquinone across SCCS product categories, with measured dermal absorption where available.
Sensitization Profile
Contact sensitization data for Hydroquinone based on clinical patch test studies and IFRA standards.
Sensitization Rate
low
Allergen Class
dye
EU Allergen Listed
no
Patch Test Positive Rate
0.3%
Cross-reactivity Group
para-amino-group
Reaction Type
contact-dermatitis
Source: IVDK; NACDG; ESSCA
Dermal Penetration Profile
Skin absorption and penetration characteristics of Hydroquinone, relevant to systemic exposure and MoS calculations.
Absorption %
35-50%
Penetration Level
dermis
Penetration Depth
epidermis/dermis
Molecular Weight
110.1 Da
Log P
0.59
Systemic Absorption
yes
Topical Bioavailability
25-45%
Safety Margin Factor
very-high
Vehicle Dependent
Yes — absorption varies by formulation
Source: SCCS Opinion
EPA ToxValDB — Toxicity Values
10 toxicity values from EPA ToxValDB (aggregated from CCTE, HPV, ToxRefDB, IRIS, and other regulatory dossiers).
| Endpoint | Value | Species | Route | Duration | Source |
|---|---|---|---|---|---|
| LOEL | =64 mg/kg-day | Rat | oral | chronic | ECOTOX |
| NOEL | =20 mg/kg-day | Rat | oral | chronic | ECOTOX |
| NOEL | =120 mg/kg-day | Mouse | oral | short-term | ECOTOX |
| LD50 | =320 mg/kg | Rat | oral | acute | NIOSH IDLH |
| LD50 | =200 mg/kg | Dog | oral | acute | NIOSH IDLH |
| LD50 | =70 mg/kg | Cat | oral | acute | NIOSH IDLH |
| NOEL | =150 mg/kg-day | Rat | oral | chronic | ECOTOX |
| NOEL | =150 mg/kg-day | Rat | oral | chronic | ECOTOX |
| NOEL | =15 mg/kg-day | Rat | oral | chronic | ECOTOX |
| NOEL | =150 mg/kg-day | Rat | oral | chronic | ECOTOX |
IARC Carcinogenicity
International Agency for Research on Cancer (WHO) monograph evaluation.
IARC Group
3
Volume
15, Sup 7, 71
Evaluation Year
1998
EU CLP Annex VI Harmonized Classification
Legally binding harmonized classification per Regulation (EC) No 1272/2008 (CLP) Annex VI.
Signal Word
Danger
Pictograms
Health HazardHarmful / IrritantCorrosiveEnvironmental Hazard
Hazard Class and Category
Carc. 2; Muta. 2; Acute Tox. 4 *; Eye Dam. 1; Skin Sens. 1; Aquatic Acute 1
Hazard Statements
- H351 Suspected of causing cancer
- H341 Suspected of causing genetic defects
- H302 Harmful if swallowed
- H318 Causes serious eye damage
- H317 May cause an allergic skin reaction
- H400 Very toxic to aquatic life
Specific Concentration Limits / M-factors
M = 10
Inserted via ATP: ATP01
Sensitization AOP Dashboard
Adverse Outcome Pathway data across 5 assays (DPRA, KeratinoSens, hCLAT, LLNA, NESIL) aggregated from public sources.
DPRA Cys %
91.45%
DPRA Lys %
52.4%
KeratinoSens IC50
130.73 µM
hCLAT CV75
5 µg/mL
LLNA EC3
0.12%
NESIL
30 µg/cm²
LLNA: Strong (1A)
GHS: 1A
Source: LLNA: Lea (1999) | Kimber et al. (1998); DPRA: Natsch et al. 2013 [DOI:10.1002/jat.2868] | Nukada et al. 2013 [DOI:10.1016/j.tiv.2012.11.006]; KS: Natsch et al. 2013 [DOI:10.1002/jat.2868]; hCLAT: Ashikaga et al. 2010 [DOI:10.1177/026119291003800403] | Sakaguchi et al. 2010 [DOI:10.1016/j.tiv.2010.05.012]
Endocrine Disruptor Evidence (Expanded)
Cross-referenced EDC classifications, mechanism data, and dose-response evidence from EDLists, SIN List, and cosmetic-specific detail sources.
Cosmetic-Specific Mechanism
Category: other
Receptor targets: ERα, AhR
LOEC: 1 µM
EU status: banned in cosmetics (Annex II)
modulator; aryl hydrocarbon receptor agonist
ECHA REACH Registration
European Chemicals Agency REACH dossier and Substances of Very High Concern listing.
Registration Type
Full
Tonnage Band
10,000 - 100,000 tonnes
Substance Type
SUBSTANCE
SVHC Candidate
No
Hazard classification: Restricted (Annex XVII)
EU CosIng Annex Listing
European Commission CosIng database Annex references per Regulation (EC) No 1223/2009.
Annex II — Prohibited
Ref: 1339
(EC) 2013/344
CMR: Carcinogenic Cat. 2(),Mutagenic Cat. 2()
Expanded Jurisdictional Detail
Additional regulatory detail beyond the 7-jurisdiction summary: Saudi SFDA, Korea MFDS, ASEAN ACD, Japan/Korea, Brazil/India, and cross-jurisdictional restriction entries.
SA Saudi SFDA (II - Prohibited)
ASEAN Cosmetic Directive (II)
Ref: 1339
JPKR Japan/Korea Cosmetics
Korea (Prohibited): ; Category: General
Korea (Restricted): max 2%
BRIN Brazil/India Cosmetics
Brazil: Prohibited
India: Prohibited (GNRAS)
India: Restricted · max 0.02% (after mixing for use)
Additional Jurisdictional Restrictions (10)
| Jurisdiction | Status | Max % | Product Type |
|---|---|---|---|
| CN | banned | - | - |
| CN | restricted | 0.3 | Oxidative hair dye products only |
| CN | permitted_hair_dye | 0.3 | Oxidative hair dye ONLY |
| IN | banned | - | all OTC cosmetics — drug classification |
| IN | drug_classification | - | skin-lightening / fairness products |
| AU | restricted | 2.0 | skin lightening |
| GCC | banned | - | All cosmetics |
| SA | banned | - | All cosmetic products |
Expanded Dermal Absorption Data
Cross-database dermal penetration: EPA Dryad physics-based, Roberts Mendeley permeation, and SCCS-aggregated measured values.
EPA Dryad Skin Absorption (physics-based)
MW: 110.111
LogP: 1.61078
Kp epidermis: 0.00383 cm/h
% dose epidermis: 0.97%
% dose stratum corneum: 1.14%
% dose dermis: 0.93%
Source: EPA Dryad Skin Absorption 2024
Roberts Skin Permeation (Mendeley 2022)
MW: 110.11
Log Kow: 0.62
Log Kp: -5.0301183562535
Log Jmax: -9.129441012722962
Source: Roberts Cheruvu Mendeley 2022
Aggregated DA Values (2 records across 5 sources)
| Type | DA % | Method | Skin Model | SCCS Ref |
|---|---|---|---|---|
| measured_in_vitro | 11.0 | In vivo — clinical (urine excretion) In vitro — Franz cells | - | Bucks et al. 1988; CIR Amended SA 2014 (1988) |
| measured_in_vitro | 42.5 | - | - | SCCS/1444/11 |
Additional Ingredient Properties
10 property records from structured ingredient metadata.
allergen_detail
{"eu_allergen_listed": "no", "allergen_class": "dye", "cross_reactivity_group": "para-amino-group", "patch_test_frequency_pct": "0.3", "sensitization_rate": "low", "common_reaction_type": "contact-dermatitis", "ifra_restricted": "no", "source": "IVDK; NACDG; ESSCA"}
anti_aging
{"anti_aging_claim": "brightening, dark-spot-reduction", "mechanism_of_action": "Bioactive compound, specialized mechanism", "target_skin_layer": "epidermis, dermis", "collagen_stimulation": "Mild", "elastin_protection": "Mild", "wrinkle_reduction_pct": "15-35", "clinical_study_duration_weeks": "12", "sample_size": "35", "double_blind": "Yes", "placebo_controlled": "Yes", "published_journal": "JAA…
baby_pediatric
{"cas_number": "123-31-9", "ingredient_class": "other", "pediatric_safety_rating": "contraindicated", "minimum_age_months": "0", "neonatal_safe": "no", "premature_infant_safe": "no", "skin_barrier_maturity_consideration": "CONTRAINDICATED: Skin bleaching, ochronosis risk, carcinogen concerns", "transepidermal_absorption_risk_pediatric": "high", "systemic_exposure_concern_pediatric": "high", "dose_…
dermal_absorption
{"molecular_weight_da": "110.1", "log_p_value": "0.59", "skin_penetration_level": "dermis", "penetration_depth": "epidermis/dermis", "absorption_pct": "35-50", "systemic_absorption": "yes", "penetration_enhancer": "no", "occlusion_effect": "no", "vehicle_dependent": "yes", "skin_barrier_effect": "weakens", "bioavailability_topical_pct": "25-45", "safety_margin_factor": "very-high", "source": "SCCS…
ecotoxicity
{"biodegradable": "partial", "biodegradation_days": "60-120", "bioaccumulative": "yes", "aquatic_toxicity_level": "high", "coral_reef_safe": "no", "marine_toxicity": "toxic to aquatic life", "freshwater_toxicity": "highly toxic", "endocrine_disruptor": "suspected", "persistent_organic_pollutant": "yes", "microplastic": "no", "nano_particle": "no", "hawaii_banned": "no", "eu_restricted_environmenta…
interactions
{"ingredient_2": "Air (oxygen)", "interaction_type": "destabilizing", "severity": "caution", "effect": "Oxidation to benzoquinone, brown discoloration", "recommendation": "Antioxidants and airless packaging required", "data_source": "Formulation science literature, dermatological research, cosmetic chemistry best practices", "last_updated": "2026-03-05"}
pediatric_safety
{"safe_for_newborn_0_6m": "avoid", "safe_for_infant_6_12m": "avoid", "safe_for_toddler_1_3y": "avoid", "safe_for_child_3_12y": "avoid", "safe_for_teen_12_18y": "avoid", "pediatric_max_concentration_pct": "0.0", "adult_max_concentration_pct": "2.0", "pediatric_dermal_absorption_factor": "very high", "immature_skin_barrier_risk": "very high", "oral_ingestion_risk": "high", "eye_irritation_risk": "hi…
pregnancy_detail
{"pregnancy_safe": "avoid", "breastfeeding_safe": "avoid", "trimester_restriction": "all", "risk_category": "FDA-C", "reason": "35-45% systemic absorption; insufficient fetal safety data", "alternative_ingredient": "Arbutin; Vitamin C; Kojic Acid", "source": "ACOG; AAD; PMC3114665"}
Function Categories & List Membership
Cosmetic/Chemical Function Categories
Antioxidant
Bleaching agent
Dye
Flavouring and nutrient
Fragrance
Monomers
Reducing agent
Stabilizing agent
Regulatory List Membership (3)
EU Banned in Cosmetics
FDA Indirect Food Contact Additives
EU CosIng Cosmetics Ingredient Database
Expert Verdict
Expert safety assessment and concern-level summary for Hydroquinone.
Regulatory Flags
eu-banned
annex-ii-prohibited
us-prescription-only
cares-act-2020
rx-4pct-us
ochronosis-risk
leukoderma-risk
cytotoxic
carcinogenicity-concern
mutagenicity-concern
para-benzoquinone-intermediate
banned-japan-australia-nz
benchmark-only
not-for-cosmetic-formulation
avoid
minamata-public-health-concern
endocrine_disruptor
eu_banned_cosmetics
eu_cosing_listed
NOAEL Studies Summary
View details ->Public NOAEL study rows linked to Hydroquinone by CAS number or substance name.
Studies
12
Lowest NOAEL
73.9
Highest NOAEL
4800
Units vary across source rows: mg/kg bw/day, mg/kg
ECHA
CIR Safety Assessment
Dermal Absorption
View details ->| Absorption % | Method | Vehicle |
|---|---|---|
| 11.0 | In vivo — clinical (urine excretion) In vitro — Franz cells | Aqueous solution (in vivo); Various |
| 42.5 | - | - |
Known Synonyms
1,4-Benzenediol
Dihydroxybenzene
Benzene, p-dihydroxy-
Black and White Bleaching Cream
Derma-Blanch
EINECS 204-617-8
Hidroquinone
NCI-C55834
para-Dihydroxybenzene
para-Dioxybenzene
para-Hydroquinone
Pyrogentistic acid
Tequinol
USAF EK-356
1,4-Dihydroxy-benzeen
UNII-XV74C1N1AE
Epiquin
Sunvanish
1,4-Dihydroxy-benzol
Chemical Function
Stabilizing agent
Antioxidant
Fragrance
Dye
Reducing agent
Bleaching agent
Flavouring and nutrient
Monomers
Regulatory Lists
banned; Europe; Personal care
CEDI
Indirect additives food contact (10/2018)
Australia; Food and drug - smoking-related products
Europe; Personal care; restricted
Canada; pharmaceutical
Canada; pharmaceutical
Danish Environmental Protection Agency
Personal care; Southeast Asia
Europe; Food contact items; Toys and children's products
Europe
inert_ingredient; non_food_use; Pesticides
drinking_water; Europe; manufacturing; plastic_additive
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
HYDROQUINONE
ChEMBL ID
CHEMBL537
Max Phase
4
Adverse Event Associations
55
Frequently Asked Questions
Is Hydroquinone allowed in the EU?
Hydroquinone EU regulatory status: prohibited. This is based on EU Regulation 1223/2009 and its amendments.
What does Hydroquinone do in cosmetics?
Hydroquinone functions as: Tyrosinase inhibitor; competitive inhibitor and cytotoxic agent to melanocytes; inhibits both melanin synthesis and DNA synthesis in melanocytes; benchmark for all modern depigmenting actives. It is classified as a Active Ingredient in our database. CAS number: 123-31-9.
What is the NOAEL for Hydroquinone?
The NOAEL (No Observed Adverse Effect Level) for Hydroquinone is =3840 mg/kg based on a general toxicity study via dermal route in rat. A total of 10 study endpoints are available. Source: CIR Safety Assessment.
Is Hydroquinone used outside cosmetics?
Hydroquinone 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 Hydroquinone have different safety status in cosmetics vs industrial chemicals?
Hydroquinone is prohibited in EU cosmetics but has active industrial GHS classifications (H302, H312, H317, H318, H341, H351, H400, H410).
Compliance Tools
Check Hydroquinone 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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