Is Hydroxyproline safe in cosmetics?
Hydroxyproline has a safety rating of "MODERATE" in our database. EU status: permitted. US status: permitted. 1 toxicological study endpoint(s) are available in our database.
Hydroxyproline
Also known as: L-Proline, 4-hydroxy-, (4R)-, (4R)-4-hydroxy-L-proline
INCI: HYDROXYPROLINE
Hydroxyproline (CAS 51-35-4) is a cosmetic cosmetic ingredient functioning as Antistatic, Hair Conditioning, Skin Conditioning, Surfactant - Cleansing. NOAEL 200 mg/kg bw/day (cross-referenced against ToxValDB ECHA IUCLID); EU Regulation 1223/2009 status: permitted. 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 51-35-4 →
Auto-generated CPSR Part A draft with source citations
Function
Antistatic, Hair Conditioning, Skin Conditioning, Surfactant - Cleansing
Safety Rating
MODERATE
Chemistry & Identifiers
IUPAC Name
(2S,4R)-4-hydroxypyrrolidine-2-carboxylic acid
InChIKey
PMMYEEVYMWASQN-DMTCNVIQSA-N
Regulatory Status
EU EU Status
permitted
US US Status
permitted
US Notes
Allowed - no prohibition or restriction; not a color additive
For full compliance data across multiple jurisdictions, use the Substance Compliance tool.
Safety Data
Margin of Safety, dermal absorption, and sensitization profile summaries for Hydroxyproline.
Calculate MoS for your specific formulation with the MoS Calculator.
Toxicological Studies
1 study endpoint found for Hydroxyproline. 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 | =200 mg/kg bw/day | oral | Rat | short-term | ToxValDB_ECHA_IUCLID |
Pre-Calculated Safety Assessment
Pre-calculated NOAEL → SED → MoS audit trail for Hydroxyproline across SCCS product categories, with measured dermal absorption where available.
ECHA REACH Registration
European Chemicals Agency REACH dossier and Substances of Very High Concern listing.
Registration Type
Full
Tonnage Band
1 - 10 tonnes
Substance Type
SUBSTANCE
SVHC Candidate
No
Additional Ingredient Properties
2 property records from structured ingredient metadata.
amino_acid
{"cas_number": "51-35-4", "ingredient_class": "amino_acid", "source_origin": "animal", "molecular_weight_range_Da": "131", "amino_acid_composition_key": "pure_hydroxyproline", "isoelectric_point": "5.8", "charge_at_pH_5_5": "zwitterionic", "water_solubility": "soluble", "oil_solubility": "insoluble", "film_forming_ability": "moderate", "moisture_binding_capacity": "excellent", "NMF_component": "no…
anti_aging
{"anti_aging_claim": "collagen-boosting", "mechanism_of_action": "Building block for proteins, NMF component", "target_skin_layer": "epidermis", "collagen_stimulation": "Yes", "elastin_protection": "Mild", "wrinkle_reduction_pct": "10-18", "clinical_study_duration_weeks": "8", "sample_size": "25", "double_blind": "Yes", "placebo_controlled": "Yes", "published_journal": "Int J Cosmet Sci", "improve…
Function Categories & List Membership
Cosmetic/Chemical Function Categories
Anti-static agent
Softener and conditioner
Surfactant (surface active agent)
Regulatory List Membership (1)
FDA Substances Added to Food (EAFUS)
Expert Verdict
Expert safety assessment and concern-level summary for Hydroxyproline.
Regulatory Flags
natural-origin
fda_food_additive
NOAEL Studies Summary
View details ->Public NOAEL study rows linked to Hydroxyproline by CAS number or substance name.
Studies
1
Lowest NOAEL
200 mg/kg bw/day
Highest NOAEL
200 mg/kg bw/day
ToxValDB_ECHA_IUCLID
Known Synonyms
L-Proline, 4-hydroxy-, (4R)-
(4R)-4-hydroxy-L-proline
Chemical Function
Surfactant (surface active agent)
Anti-static agent
Softener and conditioner
Regulatory Lists
Canada; pharmaceutical
food_additive; Substances Added to Food (formerly EAFUS) (2/2019)
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.
ChEMBL ID
CHEMBL352418
Frequently Asked Questions
Is Hydroxyproline allowed in the EU?
Hydroxyproline EU regulatory status: permitted. This is based on EU Regulation 1223/2009 and its amendments.
What does Hydroxyproline do in cosmetics?
Hydroxyproline functions as: Antistatic, Hair Conditioning, Skin Conditioning, Surfactant - Cleansing. It is classified as a cosmetic ingredient in our database. CAS number: 51-35-4.
What is the NOAEL for Hydroxyproline?
The NOAEL (No Observed Adverse Effect Level) for Hydroxyproline is =200 mg/kg bw/day based on a short-term study via oral route in Rat. Source: ToxValDB_ECHA_IUCLID.
Is Hydroxyproline used outside cosmetics?
Hydroxyproline 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.
Compliance Tools
Check Hydroxyproline 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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