Toxic Ingredient Checkers and Cosmetic Score Databases vs EU Rules: What Each One Actually Tells You

Type a cosmetic ingredient name into a search engine and the top results are usually a toxic ingredients checker or carcinogen checker: a hazard-score database that assigns the ingredient a number or a color, or a forum post repeating that number. Type the same name into EU law and you get something structurally different: a permitted-use entry with a concentration limit, or silence. Neither format tells a reader the same thing, and treating them as interchangeable is where most confusion about "toxic" ingredients starts.

This article lays out, using only each source's own published material, what a hazard-score checker is actually built to measure, what EU cosmetics law evaluates instead, and how to check properly whether an ingredient is a classified carcinogen. It ends with two worked examples pulled from cosingchecker.com's own data: methylchloroisothiazolinone and polysorbate 20.

Hazard vs risk: the distinction EU law is built on

The Scientific Committee on Consumer Safety (SCCS) evaluates cosmetic ingredients for the European Commission, and its methodology documents are explicit about a distinction that most hazard-score checkers do not carry: hazard is an intrinsic property of a substance (does it have the capacity to cause harm, under some exposure, in some test system), while risk is the probability that harm actually occurs under real conditions of use. A substance can have a hazardous property and still be used safely at a controlled concentration, in a controlled product type, with a controlled exposure route — or it can have no known hazardous property and still be used unsafely if handled wrong.

SCCS safety opinions translate this into arithmetic through the margin of safety (MoS): a toxicological point of departure from animal or non-animal test data is divided by the estimated systemic exposure dose a person would actually receive from using the product as intended. For most threshold effects the MoS calculation draws on oral toxicity data, adjusted for dermal absorption, unless robust dermal data exist. For non-threshold effects such as certain carcinogenic mechanisms, SCCS instead works from a benchmark dose (commonly BMD10) to characterize lifetime risk directly, rather than applying a safety margin. This is a risk assessment, not a hazard listing: the same molecule can return a different MoS, and a different regulatory outcome, depending on the concentration and product type it is assessed in.

How EU law actually evaluates a cosmetic ingredient

Regulation (EC) No 1223/2009 does not publish a single toxicity score for each ingredient. It works through several distinct mechanisms that sit alongside each other:

• Annexes II-VI of the Regulation, which prohibit substances (Annex II), restrict substances to a concentration and product-type condition (Annex III), or positive-list colorants, preservatives and UV filters with their own conditions (Annexes IV, V, VI). An ingredient can appear in more than one of these annexes for different uses.
• SCCS opinions, published per substance or substance group, documenting the hazard data reviewed and the margin-of-safety or benchmark-dose conclusion that supports (or does not support) a given annex entry.
• The cosmetic product safety report required under Article 10 and Annex I of Regulation (EC) No 1223/2009. Before any product is placed on the EU market, the responsible person must have it safety-assessed by a qualified assessor (a university qualification in pharmacy, toxicology, medicine or a similar discipline), taking into account the product's intended use and the anticipated systemic exposure to each ingredient in the finished formulation, using a weight-of-evidence approach across all available data. This report is product-specific and formulation-specific — it is not a per-ingredient score, and it is not published for public lookup.

The consequence for anyone reading a rule at ingredient level: an Annex III restriction with a concentration limit is binding law for that use, but it says nothing about whether a different product type, a different concentration, or a mixture with other ingredients is safe — that judgment sits inside the product-specific safety report, which the annex system does not replace. cosingchecker.com/checker/ lets you search across the CosIng inventory and Annexes II-VI for exactly this kind of record; a hit there is identity evidence for a rule, not a verdict on a finished product.

How hazard-score databases describe their own methods

Two widely used ingredient-lookup tools illustrate what a hazard score is designed to answer, in their own published terms.

EWG's Skin Deep database gives ingredients and products a two-part rating: a hazard score and a separate data-availability rating. The hazard score reflects known and suspected hazards associated with an ingredient's published research record; the data-availability score reflects how much published literature exists to support that rating at all. A product's hazard score is not a simple average of its ingredients' scores — EWG describes calculating it with a weight-of-evidence approach across all the hazards associated with the formula, benchmarked against other products in the same database. Because the second number tracks how much research exists rather than how safe an ingredient is, EWG's own guidance is to read the two ratings together, not the hazard number alone.

CosDNA publishes three separate indicators per ingredient on its FAQ page: a comedogenicity score, an irritancy score, and a Safety Level running from 1 to 10, where lower numbers indicate higher safety. CosDNA describes the Safety Level as different in kind from the other two: it is meant to evaluate long-term cumulative safety rather than a short-term reaction, and is built from adverse-effect reports drawn from sources it names as the Cosmetic Ingredient Review (CIR), RTECS, and the FDA. CosDNA's own page adds two caveats worth carrying forward: standards vary across the organizations it draws from, so it recommends using the Safety Level as a reference rather than a strict exclusion rule, and a blank field for an ingredient means no data was available to score — not that the ingredient is safe.

Both tools are transparent that their number is a literature-derived, weight-of-evidence hazard indicator, tied to how much has been published about an ingredient, not a formulation-specific, concentration-specific risk conclusion of the kind an SCCS opinion or an Article 10 safety report produces. That is a difference in what the two kinds of source are built to do, not a claim that either one is wrong at its own job.

Checking whether an ingredient is a classified carcinogen, properly

"Is this a carcinogen" has a specific legal answer in the EU, separate from any hazard-score checker: has the substance received a harmonised classification for carcinogenicity under the CLP Regulation, (EC) No 1272/2008? Harmonised classifications are set at EU level (not left to individual suppliers) and are listed in Table 3 of Part 3 of Annex VI to CLP, which is amended roughly annually, sometimes more than once a year, through Adaptation to Technical Progress (ATP) regulations following scientific opinions from ECHA's Committee for Risk Assessment. ECHA also maintains the public Classification & Labelling (C&L) Inventory, which additionally shows industry-notified classifications for substances that do not (yet) have a harmonised entry — useful context, but not itself a harmonised legal classification.

For cosmetics specifically, a CLP carcinogen, mutagen or reprotoxicant (CMR) classification feeds into Article 15 of Regulation (EC) No 1223/2009, which sets out when and how CMR-classified substances can still be used in cosmetic products — the mechanism is covered in detail in cosingchecker.com/blogs/cmr-substances-eu-cosmetics-article-15-explained/ and is not repeated here. The practical sequence for checking an ingredient is: identify it by CAS or EC number, check Annex VI of CLP (or the ECHA C&L Inventory) for a harmonised carcinogenicity classification, and if one exists, check whether and how Article 15 and the CosIng annexes have been applied to that CAS number for cosmetic use.

Worked example 1: methylchloroisothiazolinone (with methylisothiazolinone)

cosingchecker.com's data for methylchloroisothiazolinone (CAS 26172-55-4, EC 247-500-7) resolves to CosIng reference 35333 and to Annex V entry 39, listed jointly as "Methylchloroisothiazolinone and Methylisothiazolinone." The Annex V record permits the mixture as a preservative in rinse-off products only, at a maximum concentration of 0.0015% (in the fixed 3:1 ratio of the two substances), under Regulation (EU) No 1003/2014, and the entry's own SCCS-opinion history lists five separate SCCS/SCCNFP opinions behind it, including a 2013 clarification and a dedicated methylisothiazolinone-only sensitisation opinion. That is a chain of hazard review followed by a risk-based, product-type-specific and concentration-specific rule — not a single score.

cosingchecker.com's jurisdiction data for this same CAS number also shows the same 0.0015% rinse-off ceiling carried into Great Britain's post-Brexit Annex V and into the ASEAN Cosmetic Directive Annex VI, while Health Canada's Hotlist restricts the combination to rinse-off use at 0.0015% and prohibits it in leave-on products, and Australia's Poisons Standard places it in Schedule 6 with its own rinse-off/leave-on split. The rule is broadly consistent in direction across these markets but is not one global number — each jurisdiction publishes its own binding text, and cosingchecker.com/checker/ is built to surface each one by CAS number rather than merge them. A full deep-dive on this preservative pair, including the methylisothiazolinone-only entries, is a separate sibling article; this section only establishes how the EU record itself reads.

Worked example 2: polysorbate 20

Polysorbate 20 (CAS 9005-64-5), CosIng reference 79318, functions in CosIng as a cleansing and emulsifying surfactant. Querying cosingchecker.com's own data for this CAS number returns zero EU annex evidence entries and zero jurisdiction rule records: it does not appear in Annexes II-VI, and none of the 13 markets in cosingchecker.com's jurisdiction data carry a specific binding or guidance record for it. Per the site's own stated disclaimer on that endpoint, absence of a record is not evidence that a substance is prohibited or permitted — it means no annex or jurisdiction record for that identifier exists in the data today. An unrestricted-use surfactant with a long safety-assessment history through other channels (such as CIR) is exactly the kind of ingredient where a checker built to answer "is there a specific EU cosmetics rule for this identifier" and a checker built to answer "what published hazard literature exists for this identifier" can legitimately return different kinds of answers, because they are built to answer different questions.

Reading the two kinds of source together

A hazard-score checker like EWG Skin Deep or CosDNA is answering: given the published literature this database has reviewed, what hazards has this ingredient been associated with, and how much data backs that up? EU cosmetics law, through the CosIng annexes, SCCS opinions, and the Article 10 safety report, is answering a narrower and more specific question: for this substance, at this concentration, in this product type, has a documented risk assessment concluded the use is acceptable? A classified carcinogen under CLP Annex VI is a third, separate legal fact, checkable at ECHA independent of either. None of the three substitutes for the others, and none of them is a verdict a reader can extend past what it was built to answer — cosingchecker.com/sources/ documents which official registers this site's own data is built from, for readers who want to verify any of the records above at the primary source.

Sources

• SCCS Notes of Guidance for the Testing of Cosmetic Ingredients and their Safety Evaluation, 12th revision (SCCS/1647/22) — https://health.ec.europa.eu/publications/sccs-notes-guidance-testing-cosmetic-ingredients-and-their-safety-evaluation-12th-revision_en
• Regulation (EC) No 1223/2009, Article 10 and Annex I (cosmetic product safety report) — https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:02009R1223-20240301
• Regulation (EC) No 1223/2009, Article 15 (CMR substances) — https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:02009R1223-20240301
• Regulation (EC) No 1272/2008 (CLP), Annex VI, Part 3, Table 3 (harmonised classification and labelling) — https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32008R1272
• ECHA, Classification and Labelling (C&L) Inventory — https://echa.europa.eu/information-on-chemicals/cl-inventory-database
• ECHA, CLP legislation overview — https://echa.europa.eu/regulations/clp/legislation
• EWG Skin Deep, Understanding Skin Deep Ratings — https://www.ewg.org/skindeep/understanding_skin_deep_ratings/
• CosDNA, FAQ: Explanation of Comedogenicity, Irritancy, and Safety Level — https://www.cosdna.com/eng/help/ingredients_qna.php
• cosingchecker.com API, ingredient record and jurisdiction rules for methylchloroisothiazolinone (CAS 26172-55-4) — https://cosingchecker.com/api/v1/ingredients/35333-methylchloroisothiazolinone/jurisdictions/
• cosingchecker.com API, ingredient record for polysorbate 20 (CAS 9005-64-5) — https://cosingchecker.com/api/v1/ingredients/79318-polysorbate-20/jurisdictions/
• cosingchecker.com, CMR substances and Article 15 explained — https://cosingchecker.com/blogs/cmr-substances-eu-cosmetics-article-15-explained/
• cosingchecker.com, Checker tool — https://cosingchecker.com/checker/
• cosingchecker.com, Sources — https://cosingchecker.com/sources/