Ingredient deep-dive

Cyclopentasiloxane (D5): Is It a Microplastic?

Sources reviewedSilicone

Cyclopentasiloxane (D5) is a cyclic silicone distinct from Dimethicone and the Cyclomethicone mixture name. The reviewed fluid description is not a solid-particle measurement of your product, and EU restrictions apply independently.

Shared method updated October 6, 2026. Individual sources reviewed October 6, 2026.

What changed in this reference

Earlier pages inferred a yes/no microplastic verdict from an editorial high/medium/low grouping. Those labels were not measurements or health-risk grades. The shared answer, FAQ and regulation context now distinguish label names from physical particles. This entry also received the individual source review described below.

Cyclopentasiloxane, also called decamethylcyclopentasiloxane or D5, is a five-unit cyclic dimethyl siloxane. CIR describes a fluid and historical conditioning and solvent functions; current EU rules require a separate check.

Identity corrections and evidence limits

The earlier backbone-based non-microplastic verdict is withdrawn. REACH entry 70 restricts placing D5 wash-off cosmetics on the market at 0.1% or more by weight after 31 January 2020 and applies its other cosmetic scope after 6 June 2027, subject to the full entry. These are legal thresholds, not health-based safe amounts.

The CIR cyclic-siloxane assessment supplies identities and historical cosmetic functions. Its use-scoped conclusion predates the current EU restrictions; it cannot establish current permission, a product-specific exposure level or environmental safety.

Reported uses and functions

Historical hair-conditioning and emollient functions
Historical solvent function

How the rules depend on the product

European Union

D4, D5 and D6 have a separate REACH restriction in entry 70. Its general threshold is 0.1% or more by weight of each substance after 6 June 2026. The D4/D5 wash-off provision applies after 31 January 2020; paragraph 3(b) defers other specified cosmetic scope until after 6 June 2027. Product scope and derogations must be checked in the full entry. D4 is also prohibited as a cosmetic ingredient under Annex II, entry 1388; the REACH threshold does not override that prohibition.

United States

The federal Microbead-Free Waters Act targets intentionally added solid plastic microbeads in rinse-off cosmetics for exfoliating or cleansing. It is not a blanket ban on all polymers or a product safety assessment. Other applicable rules require separate checking.

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Cyclopentasiloxane (D5), common questions

Is Cyclopentasiloxane (D5) a microplastic?

Does a label match mean Cyclopentasiloxane (D5) is banned?

A label match alone cannot determine product compliance. EU context: D4, D5 and D6 have a separate REACH restriction in entry 70. Its general threshold is 0.1% or more by weight of each substance after 6 June 2026. The D4/D5 wash-off provision applies after 31 January 2020; paragraph 3(b) defers other specified cosmetic scope until after 6 June 2027. Product scope and derogations must be checked in the full entry. D4 is also prohibited as a cosmetic ingredient under Annex II, entry 1388; the REACH threshold does not override that prohibition. US context: The federal Microbead-Free Waters Act targets intentionally added solid plastic microbeads in rinse-off cosmetics for exfoliating or cleansing. It is not a blanket ban on all polymers or a product safety assessment. Other applicable rules require separate checking. Other substance-specific rules are separate from the microplastic definition; this reference is not a compliance determination.

Can a label show the particle count or health effect?

A label-name match does not measure particles, concentration, exposure or health effects. Polymer identity alone does not establish particle form or legal scope.

Sources and review scope

The Commission guide establishes the shared definition and transition context; CosIng inclusion is not ingredient approval. Label rules do not provide a particle assay. Ingredient-specific sources support the identity and scope stated here, not a tested product or measured health outcome.