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Decamethylcyclopentasiloxane

CAS 293-51-6 · 100/100 · High conf.

Also registered as 4 other CAS numbers

540-97-6 · 541-02-6 · 556-67-2 · 69430-24-6

Decamethylcyclopentasiloxane chemical structure

Concern score

100/100Critical concern driven by cmr.
High confidence

Decamethylcyclopentasiloxane in plain language

What it is

On cosmetic ingredient lists it appears as “Cyclohexasiloxane”.

Also known as Cyclohexasiloxane · Cyclomethicone · Cyclopentasiloxane · Cyclotetrasiloxane · Cyclomethicone 5 · Octamethylcyclotetrasiloxane; D4

Show all 39 names

Ciclopentasiloxane · Cyclomethicone D5 · Cyclopentasiloxane (D5) · Octamethylcyclotetrasiloxane (D5) · Botanisil CP 33 · Cyclic dimethylsiloxane pentamer · Cyclo-decamethylpentasiloxane · Cyclopentadimethylsiloxane · Cyclopentasiloxane, 2,2,4,4,6,6,8,8,10,10-decamethyl- · Cyclopentasoloxane · D5 · D5-sil · Dow corning st cyclomethicone 5 · Dow corning UP-1002 ultra pure fluid · Dekamethylcyklopentasiloxan · Dimethylsiloxane pentamer · Dodecamethylcyclohexasiloxane · Dow corning 345 · Jeesilc CPS-211 · KF-995 · Lightening Serum · NUC silicone VS 7158 · Octamethylcyclotetrasiloxane · Sf 1202 · Silicon SF 1202 · Vs 7158 · Xiameter PMX-0245 · cyclopentasiloxa ne · d5decamethyl-cyclopentasiloxane · decamethyl cyclopentasiloxane · decamethylcyclopenta- siloxane · decamethylcyclopentasiloxane (D5) · KP-545 component cyclomethicone 5

What it does

Used in cosmetics as an emollient, a solvent and a skin-conditioning agent. Cyclohexasiloxane is the cyclic dimethyl polysiloxane.

  • Emollient
  • Solvent
  • Skin conditioning
  • Hair conditioning
  • Emulsifier
  • Film former
Is it a concern?
Critical concern: classified for carcinogenic, mutagenic or reproductive toxicity (CMR). It is banned in EU cosmetics.

Why it's flagged

  • Cmr

Octamethylcyclotetrasiloxane; D4 is prohibited in cosmetic products under Annex II of the EU Cosmetics Regulation (EC) 1223/2009.

RestrictedEU EC — banned

The score describes this ingredient's chemical identity — its hazard profile from published classifications and regulatory status — not the safety of any product it appears in.

Regulation

Restrictions first, then routine listings from published regulatory sources.

  • In marketed US drugs
  • EU Annex II — prohibited
  • EU prohibited in cosmetics
  • Inactive ingredient in US drugs

Recorded in these product areas

  • Found in consumer products
  • Beauty
  • Cleaning
  • Pharma
  • Food
  • Industrial

  • EUEC

    Annex II of EU Cosmetics Regulation (EC) 1223/2009: substances prohibited in cosmetic products. CMR: Reprotoxic Cat. 2()

    banned
    View source →
  • EUCosIngActive5 entries
    • 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%.Source →
    • 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.Source →
    • Cyclopentasiloxane is the cyclic dimethyl polysiloxane that conforms to the formula:Source →
    • Cyclotetrasiloxane is the cyclic dimethyl polysiloxane that conforms to the formula: Restriction: II/1388Source →
    • Cosmetics Regulation annex II / ref 1388.Source →
  • USFDAinactive ingredient database3 entries
    • Route: TOPICAL; Dosage form: AEROSOL; Potency: 2.5 %w/wSource →
    • Route: TOPICAL; Dosage form: AEROSOL, FOAM; Maximum daily exposure: 144 mgSource →
    • Route: TOPICAL; Dosage form: CREAM, AUGMENTED; Maximum daily exposure: 260 mgSource →
  • EUEFSAEFSA opinionScientific 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)
    • 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)Source →
  • USEPAcommercial use observedEPA 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.
    • 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.Source →
  • USFDAmarketed drug occurrenceFDA NDC lists this ingredient in 1 active drug products and 1 total products.
    • FDA NDC lists this ingredient in 1 active drug products and 1 total products.Source →
  • USFDAlisted in openFDA substanceopenFDA substance registry classifies this ingredient as chemical.
    • openFDA substance registry classifies this ingredient as chemical.Source →

Expert safety opinions

Independent scientific assessments cited by the records we hold, with the year and link where the record gives one.

  • SCCS

    EU Scientific Committee on Consumer Safety

    No SCCS opinion on file.

  • CIR

    Cosmetic Ingredient Review (US expert panel)

    No CIR safety assessment 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 · EU EFSA listing · Read the source →

Evidence & sources

No graded research studies for Decamethylcyclopentasiloxane yet. This record is compiled from the published data sources below — registries and regulatory listings, not study findings.

10 data sources

Where this comes from

  • CosIng

    regulatory · updated 2026-09-23

    Open →

  • EU CosIng Cosmetics Regulation Annexes

    regulatory · updated 2020-07-30

    Open →

  • EFSA OpenFoodTox

    regulatory · updated 2026-10-04

    Open →

  • EPA Chemical and Products Database

    exposure · updated september 5, 2012

    Open →

  • EPA DSSTox Identifiers

    chemistry · updated 2025-12-29

    Open →

  • FDA Inactive Ingredient Database

    regulatory · updated 2026-01-09

    Open →

  • FDA National Drug Code Directory

    regulatory · updated 2026-12-31

    Open →

  • FDA GSRS UNII

    registry · updated 2026-02-26

    Open →

  • openFDA Substance

    registry · updated 2026-05-24

    Open →

  • PubChem Live Enrichment

    chemistry · updated 2026-05-17

    Open →
Reference links (4)
Openfda substance

siltechpersonalcare.com

Read →

Suitability

Context-specific fit derived from published classifications and the current ingredient evidence profile.

Food use

Food-use source coverage is present in the current record.

Good fit

The ingredient appears in food-oriented source coverage or allowed-use references, which makes food use easier to support than a context with no domain signal at all.

Fragrance avoidance

Not a strong fit for fragrance avoidance because it carries Fragrance.

Avoid

The ingredient itself is a fragrance-linked signal, so it is better treated as an avoid case when fragrance exposure is the main concern.

Where it has been recorded

How often EPA CPDat has listed Decamethylcyclopentasiloxane in a product composition. These are source records, not Greenveil catalog products.

Source records

9,212

Named organisations

6

Construction and building materialsIndustrial productsPersonal careHome maintenanceFood and drugConstruction

Typical roles

EmollientSolventSkin conditioningHair conditioningEmulsifierFilm former
See products using Decamethylcyclopentasiloxane →

Catalog

Found in these products

Their ingredient lists include Decamethylcyclopentasiloxane; each product's own rating depends on its whole formula, so it is shown on the product page, not here.

See all 959 →Find products without it →

Co-occurrence

Often appears with

Ingredients that frequently appear alongside Decamethylcyclopentasiloxane in the catalog.