# Decamethylcyclopentasiloxane

URL: https://app.greenveil.ai/ingredients/ingredient_dtxsid_dtxsid1027184
Categories: beauty, cleaning, food, industrial, pharma
Functions: Emollient, Solvent, Skin conditioning, Hair conditioning, Emulsifier, Film former
Identifier: DTXSID1027184

> Decamethylcyclopentasiloxane: Used in cosmetics as an emollient, a solvent and a skin-conditioning agent. Cyclohexasiloxane is the cyclic dimethyl polysiloxane. Greenveil chemical-concern score: 100/100 — Critical concern driven by cmr.. Compiled from 10 published data sources.

## Safety assessment

- Chemical concern score: 100/100 — Critical concern driven by cmr.
- Confidence in this assessment: High
- Is it a concern? Critical concern: classified for carcinogenic, mutagenic or reproductive toxicity (CMR). It is banned in EU cosmetics.
- Rationale: Octamethylcyclotetrasiloxane; D4 is prohibited in cosmetic products under Annex II of the EU Cosmetics Regulation (EC) 1223/2009.

## Regulatory status

- EU: Active — Cyclohexasiloxane is the cyclic dimethyl polysiloxane that conforms to the formula, where n equals 6, and the other components of cyclomethicone (where n equals 4, 5, or 7) are present at levels of less than 1%.
- EU: Active — Cyclomethicone is a generic name for a mixture of cyclic dimethyl polysiloxane compounds that conform to the formula, where n has a value between 4 and 6. Restriction: Entry 1388 of Annex II corresponds to D4 (Cyclotetrasiloxane). If Cyclomethicone contains D4 then entry II/1388 applies.

Restricted under COMMISSION REGULATION (EU) 2024/1328. 1. Shall not be placed on the market (a) as a substance on its own; (b) as a constituent of other substances; or (c) in mixtures; in a concentration equal to or greater than 0,1 % by weight of the respective substance after 6 June 2026. [...] 3. By way of derogation: (a) for D4 and D5 in wash-off cosmetic products, paragraph 1, point (c), shall apply after 31 January 2020. For the purposes of this point, “wash-off cosmetic products” means cosmetic products as defined in Article 2(1), point (a), of Regulation (EC) No 1223/2009 of the European Parliament and of the Council (*1) that, under normal conditions of use, are washed off with water after application; (b) for all cosmetic products other than the ones mentioned in paragraph 3(a), paragraph 1 shall apply after 6 June 2027.
- EU: Active — Cyclopentasiloxane is the cyclic dimethyl polysiloxane that conforms to the formula:
- EU: Active — Cyclotetrasiloxane is the cyclic dimethyl polysiloxane that conforms to the formula: Restriction: II/1388
- EU: Active — Cosmetics Regulation annex II / ref 1388.
- EU: banned — Annex II of EU Cosmetics Regulation (EC) 1223/2009: substances prohibited in cosmetic products. CMR: Reprotoxic Cat. 2()
- EU: EFSA opinion — Scientific Opinion on the safety evaluation of the substance, alpha-dimethyl-3-(4'-hydroxy-3'-methoxyphenyl)propylsilyloxy, omega-3-dimethyl-3-(4'- hydroxy-3'-methoxyphenyl)propylsilyl polydimethylsiloxane, n=26-50, CAS No. 156065-00-8, for use in food contact materials - EFSA Panel on food contact materials, enzymes, flavourings and processing aids (CEF) (EFSA CEF)
- US: commercial use observed — EPA CPDat observed this chemical in 9212 composition records across product categories including Construction and building materials, Industrial products, Personal care. EPA CPDat classifies this chemical for functional uses including Solvent, Lubricating agent, Emulsifier.
- US: inactive ingredient database — Route: TOPICAL; Dosage form: AEROSOL; Potency: 2.5 %w/w
- US: inactive ingredient database — Route: TOPICAL; Dosage form: AEROSOL, FOAM; Maximum daily exposure: 144 mg
- US: inactive ingredient database — Route: TOPICAL; Dosage form: CREAM, AUGMENTED; Maximum daily exposure: 260 mg
- US: marketed drug occurrence — FDA NDC lists this ingredient in 1 active drug products and 1 total products.
- US: listed in openFDA substance — openFDA substance registry classifies this ingredient as chemical.

## Expert safety opinions

- SCCS (EU Scientific Committee on Consumer Safety): no opinion on file.
- CIR (Cosmetic Ingredient Review (US expert panel)): no opinion on file.
- EFSA (European Food Safety Authority): Scientific Opinion on the safety evaluation of the substance, alpha-dimethyl-3-(4'-hydroxy-3'-methoxyphenyl)propylsilyloxy, omega-3-dimethyl-3-(4'- hydroxy-3'-methoxyphenyl)propylsilyl polydimethylsiloxane, n=26-50, CAS No. 156065-00-8, for use in food contact materials - EFSA Panel on food contact materials, enzymes, flavourings and processing aids (CEF) (EFSA CEF) — 2011 — https://doi.org/10.2903/j.efsa.2011.2402.

## Data sources

- CosIng (updated 2026-09-23): https://ec.europa.eu/growth/tools-databases/cosing/details/33101
- EU CosIng Cosmetics Regulation Annexes (updated 2020-07-30): https://ec.europa.eu/growth/tools-databases/cosing/reference/annexes/list/II
- EFSA OpenFoodTox (updated 2026-10-04): https://doi.org/10.5281/zenodo.8120114
- EPA Chemical and Products Database (updated september 5, 2012): http://siri.org/msds/f2/ckj/ckjmq.html
- EPA DSSTox Identifiers (updated 2025-12-29): https://epa.figshare.com/articles/dataset/Chemistry_Dashboard_Data_DSSTox_Identifiers_Mapped_to_CAS_Numbers_and_Names/5588566
- FDA Inactive Ingredient Database (updated 2026-01-09): https://www.fda.gov/drugs/drug-approvals-and-databases/inactive-ingredients-database-download
- FDA National Drug Code Directory (updated 2026-12-31): https://www.fda.gov/drugs/drug-approvals-and-databases/national-drug-code-directory-support-files
- FDA GSRS UNII (updated 2026-02-26): https://precision.fda.gov/uniisearch/
- openFDA Substance (updated 2026-05-24): https://api.fda.gov/other/substance.json?search=unii:0THT5PCI0R
- PubChem Live Enrichment (updated 2026-05-17): https://pubchem.ncbi.nlm.nih.gov/compound/10913

_Assessed by Greenveil._