Ingredient deep-dive

Cyclotetrasiloxane (D4): Is It a Microplastic?

Sources reviewedSilicone

Cyclotetrasiloxane (D4) is a cyclic silicone. Its EU cosmetics prohibition is separate from microplastics classification; a REACH concentration threshold is not permission to add D4 to a cosmetic.

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.

Cyclotetrasiloxane, also called octamethylcyclotetrasiloxane or D4, is a cyclic siloxane with four silicon–oxygen units and methyl groups. D4 is prohibited as an ingredient in EU cosmetics under Annex II, entry 1388.

Identity corrections and evidence limits

D4 means the four-unit cyclic identity, not every silicone polymer. The prior claim that it is merely restricted to 0.1% in cosmetics is corrected: Annex II prohibits its cosmetic-ingredient use independently. This reference does not decide the legal treatment of technically unavoidable traces.

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

Hair-conditioning, emollient and solvent functions reported historically

How the rules depend on the product

European Union

D4 is prohibited as an ingredient in EU cosmetics under Cosmetics Regulation Annex II, entry 1388. REACH entry 70 also restricts D4, D5 and D6 with concentration, use and derogation conditions; its 0.1% threshold does not override the cosmetics prohibition. A label match cannot resolve compliance or the treatment of technically unavoidable traces.

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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Cyclotetrasiloxane (D4), common questions

Is Cyclotetrasiloxane (D4) a microplastic?

Cyclotetrasiloxane (D4) is a cyclic silicone. Its EU cosmetics prohibition is separate from microplastics classification; a REACH concentration threshold is not permission to add D4 to a cosmetic.

Does a label match mean Cyclotetrasiloxane (D4) is banned?

A label match alone cannot determine product compliance. EU context: D4 is prohibited as an ingredient in EU cosmetics under Cosmetics Regulation Annex II, entry 1388. REACH entry 70 also restricts D4, D5 and D6 with concentration, use and derogation conditions; its 0.1% threshold does not override the cosmetics prohibition. A label match cannot resolve compliance or the treatment of technically unavoidable traces. 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.