COSMETIC INGREDIENT IDENTIFICATION GUIDE
Your ingredient may need both an INCI name and a CAS number, but it may not need a new application for either. INCI names support cosmetic ingredient naming and labeling; CAS numbers identify chemical substances. The right next step is to confirm what the material contains and whether existing records accurately describe it.
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Jump to the key questions before applying for an INCI name or CAS number.
What is the difference between an INCI name and a CAS number?
For suppliers preparing samples, responding to brand questionnaires or entering a new market, this distinction matters: a customer's request for both identifiers is a reason to verify the records before commissioning new applications. A trade name or a single line on a specification is rarely enough to make that decision.
| Comparison point | INCI name | CAS number |
|---|---|---|
| Purpose | Standardized cosmetic ingredient name | Identifier for a specific chemical substance |
| Assigned by | International Nomenclature Committee (INC); published by the Personal Care Products Council (PCPC) | CAS; recorded in CAS REGISTRY |
| Typical use | Ingredient lists, formula and labeling records, supplier communication | Substance searches, safety data sheets (SDS), trade, research and chemical regulatory submissions |
| Market approval? | No: does not establish safety or permission to use | No: does not establish inventory listing or regulatory registration |
INCI stands for International Nomenclature Cosmetic Ingredient. PCPC publishes the names in its ingredient dictionary, available electronically as wINCI. They help identify ingredients consistently across languages and markets. Learn more about INCI from PCPC.
A CAS Registry Number (CAS RN) is assigned by the CAS (Chemical Abstracts Service) for chemical substances included in the CAS REGISTRY database; it distinguishes a substance even when it has several chemical or common names.
Unlike either system, a trade name identifies a commercial product and is chosen by its supplier or brand. That product may contain active ingredients, solvents, preservatives and carriers.
Both systems cover more than simple chemicals. INCI names are used for materials such as botanicals, ferments, peptides, exosome ingredients and polymers. CAS REGISTRY also includes polymers and eligible complex substances, including substances of unknown or variable composition, complex reaction products or biological materials (UVCBs).
Can one INCI name have more than one CAS number?
Yes. The relationship between INCI names and CAS numbers is not always one-to-one. One INCI name may be associated with several CAS numbers, and one CAS number may be associated with several INCI names. PCPC expressly recognizes these relationships. See PCPC's INCI information.
Check the ingredient definition, source, process and composition, as relevant. A supplier document containing both an INCI name and a CAS number does not, by itself, prove that both match the material supplied.
Example: glycerin. A supplier might sell a material as "Vegetable Glycerin 99.5%," an illustrative commercial description. The INCI name is Glycerin and the CAS number for glycerin is 56-81-5. For a glycerin material without additional formulated components, these references can describe the same raw material. If the product contains added water, preservatives or other ingredients, establish the names and identifiers for those components as well.
When do customers need both identifiers?
A brand evaluating an innovative peptide, ferment, botanical extract or polymer may need the INCI name for formulation and labeling work, alongside CAS information for substance-level checks. Across international supply chains, purchasing and regulatory teams may also request CAS information for SDS, trade or chemical compliance documentation.
For a commercial blend, the response may involve several names and numbers. Map each component instead of assuming that one identifier describes everything sold under the trade name. Providing only an INCI name or only a CAS number may leave the customer's due diligence incomplete.
When should you apply for an INCI name or CAS number?
Begin by identifying the material. For a defined substance, confirm the structure, molecular formula, salt form and isomeric identity. For a botanical or other complex ingredient, establish the species, source or plant part, manufacturing process, principal composition and representative structure where applicable. For a blend, list the components and concentrations.
Next, review the actual records: the definition and source information in the wINCI monograph, and the structure, composition or substance description associated with the CAS number. A similar name is not enough to establish a match.
Both records match: A new application is generally unnecessary. Keep the search and matching evidence, then continue the target-market compliance assessment.
INCI name confirmed, CAS identity missing or uncertain: Search for an existing CAS record first. If no matching record exists, assess a new CAS number assignment.
CAS identity confirmed, no suitable INCI name: Check whether an existing monograph covers the ingredient. If none does, assess an INCI name application.
Only a similar record is available: Resolve differences in definition, source or processing before using it or applying. For a multi-component product, complete this assessment for each component.
Failure to find a name or number in a public search does not establish that no record exists. Search and verification should precede a new application.
Should you obtain the CAS number or the INCI name first?
There is no fixed order for every cosmetic ingredient. The material's identity and the records already available should determine the sequence.
For a structurally defined substance, confirming the structure and CAS identity first can support the INCI assessment. For botanical, fermentation-derived and other complex materials, prepare the shared source, process and composition information first; the two assessments may then proceed in parallel.
If an existing name or number may apply, prioritize verification. If the customer needs both, use one consistent set of identity information for PCPC, CAS and downstream customers to avoid conflicting descriptions.
What should you prepare before requesting an assessment?
A useful starting file includes the following information, where applicable:
Trade name, proposed name and any existing INCI or CAS records.
Material type: single substance, complex substance or mixture.
Chemical name, structure, sequence, species or other source information.
Manufacturing process, reactants or monomers, and extraction or fermentation details.
Full composition and concentrations, including purity, impurities, carriers and solvents.
Intended uses, target markets and the customer's specific information request.
This is an assessment checklist. The information needed for a particular application depends on the material and the route selected.
Do INCI and CAS identifiers establish regulatory compliance?
No. An INCI assignment does not establish safety or approval for cosmetic use. A CAS number does not demonstrate chemical inventory listing or completion of REACH registration, notification or other market-access procedures. See PCPC's INCI FAQs.
After confirming identity, assess the target market's applicable requirements and exemptions against the actual substance, intended use, annual volume and responsible legal entity. Check the actual supply route and any use, concentration or other restrictions. Names and numbers begin the evidence trail; they do not complete it.
Need help checking an INCI name or CAS number?
REACH24H helps cosmetic ingredient suppliers determine whether existing records apply or a search, verification or new application is appropriate. We assess the composition, structure, source, manufacturing process and intended use together, then support the relevant route:
INCI name applications: Existing-name and monograph assessment, organization of ingredient information, and application preparation, submission and follow-up.
CAS number searches, verification and applications: Existing-record matching, preparation of substance identity information, and support with the appropriate CAS search or assignment request.
Send your current specification, composition and available structure or source and manufacturing process information, along with the intended use and customer request. Our team can help clarify which route to pursue before you begin an application.
Need to confirm the right identifier route?
Share your available identity information and intended use. REACH24H can help clarify whether to verify existing records or prepare for a new request.
