Cyclopentasiloxane in Cosmetics: New Restrictions on D4, D5 and D6
Cyclopentasiloxane, Cyclotetrasiloxane and Cyclohexasiloxane are cyclic siloxanes used in cosmetic formulations, particularly to improve spreadability, lightness and the silky sensory profile of products.
From a regulatory perspective, these substances correspond to:
| INCI name | Abbreviation | Chemical name | CAS number |
|---|---|---|---|
| Cyclotetrasiloxane | D4 | Octamethylcyclotetrasiloxane | 556-67-2 |
| Cyclopentasiloxane | D5 | Decamethylcyclopentasiloxane | 541-02-6 |
| Cyclohexasiloxane | D6 | Dodecamethylcyclohexasiloxane | 540-97-6 |
Commission Regulation (EU) 2024/1328 amends Annex XVII to Regulation (EC) No 1907/2006, known as REACH, introducing new restrictions on D4, D5 and D6. Although the regulation concerns REACH rather than the Cosmetics Regulation directly, it has a significant impact on cosmetic products, especially leave-on products containing Cyclopentasiloxane or Cyclohexasiloxane.
Why Have These Restrictions Been Introduced?
The restrictions are mainly based on environmental concerns.
D4, D5 and D6 have been identified as substances of very high concern due to their persistence and bioaccumulative properties in the environment.
In particular:
- D4 – Cyclotetrasiloxane has been identified as a persistent, bioaccumulative and toxic substance (PBT) and as a very persistent and very bioaccumulative substance (vPvB);
- D5 – Cyclopentasiloxane and D6 – Cyclohexasiloxane have been identified as vPvB substances and, where they contain D4 at a concentration equal to or above 0.1% by weight, also as PBT substances.
The Regulation states that widespread uses in cosmetic products represent a major source of environmental release. The aim of the restriction is therefore to reduce emissions of these cyclic siloxanes during the life cycle of products.
What Does Regulation (EU) 2024/1328 Provide?
As a general rule, D4, D5 and D6 may not be placed on the market:
- as substances on their own;
- as constituents of other substances;
- in mixtures;
where the concentration of the respective substance is equal to or greater than 0.1% by weight.
Specific application dates apply to cosmetic products, depending on the substance and the type of product concerned.
Cyclopentasiloxane in Rinse-Off Cosmetic Products
For rinse-off cosmetic products, such as shampoos, cleansers and shower gels, the restriction concerning D5 – Cyclopentasiloxane was already applicable before Regulation (EU) 2024/1328.
Since 31 January 2020, rinse-off cosmetic products may not be placed on the market where they contain Cyclopentasiloxane at a concentration equal to or above 0.1% by weight.
| INCI name | Product type | Limit |
|---|---|---|
| Cyclopentasiloxane / D5 | Rinse-off cosmetic products | Less than 0.1% |
The earlier restriction also covered D4 in rinse-off cosmetic products. However, Cyclotetrasiloxane / D4 is already prohibited in cosmetic products under Annex II to Regulation (EC) No 1223/2009, following its inclusion through Commission Regulation (EU) 2019/831.
New Deadline for Leave-On Products and Cyclohexasiloxane: 6 June 2027
The most relevant development for cosmetic companies concerns products that were not covered by the previous D4/D5 rinse-off restriction.
After 6 June 2027:
- Cyclopentasiloxane / D5 may not be placed on the market in cosmetic products other than rinse-off products at a concentration equal to or above 0.1% by weight;
- Cyclohexasiloxane / D6 may not be placed on the market in cosmetic products at a concentration equal to or above 0.1% by weight.
| INCI name | Cosmetic products concerned | Limit after 6 June 2027 |
|---|---|---|
| Cyclopentasiloxane / D5 | Products other than rinse-off products, including leave-on cosmetics | Less than 0.1% |
| Cyclohexasiloxane / D6 | Cosmetic products | Less than 0.1% |
The concentration limit must be assessed separately for each substance. A product containing both D5 and D6 must therefore comply with the limit for each individual cyclic siloxane.
Which Cosmetic Products Should Be Checked?
The presence of Cyclopentasiloxane or Cyclohexasiloxane may be relevant in various cosmetic categories, particularly in products designed to provide a dry, silky or highly spreadable sensory effect.
Products requiring particular attention may include:
- face serums and leave-on treatments;
- primers, foundations and other make-up products;
- hair leave-on products;
- body oils and lightweight fluids;
- deodorants;
- sprays and aerosol products;
- rinse-off products containing Cyclohexasiloxane.
The review should not be limited to the ingredient list on the label. It should also include the quantitative formula and the technical documentation of raw materials.
Attention to Cyclomethicone
When reviewing formulations, attention should also be paid to Cyclomethicone.
Cyclomethicone may refer to a mixture of volatile cyclic siloxanes, which can include D4, D5 and D6 in varying proportions. The European Commission’s SCCS has described Cyclomethicone as a term covering cyclic siloxanes including Cyclotetrasiloxane, Cyclopentasiloxane and Cyclohexasiloxane.
Therefore, where Cyclomethicone appears in a formula or in raw material documentation, the supplier should be asked to confirm the possible presence and concentration of:
- Cyclotetrasiloxane / D4;
- Cyclopentasiloxane / D5;
- Cyclohexasiloxane / D6.
This information is necessary to verify compliance with the applicable limits.
REACH Restriction and Cosmetic Compliance
Regulation (EU) 2024/1328 introduces a restriction under REACH, based on the environmental risks associated with the persistence and bioaccumulation of D4, D5 and D6.
The restriction does not arise from a new assessment of consumer safety under cosmetic legislation. Nevertheless, it directly affects whether a cosmetic product may be placed on the EU market.
A cosmetic product may therefore be compliant from a safety assessment perspective, but still require reformulation if it does not comply with the REACH restriction.
What Should Cosmetic Companies Do?
Cosmetic companies, manufacturers, brand owners, importers and Responsible Persons should assess the impact of the restriction on products already marketed and on products under development.
The main actions include:
- searching formulations for Cyclopentasiloxane and Cyclohexasiloxane;
- checking raw materials identified as Cyclomethicone;
- confirming the possible presence of D4, D5 and D6 through updated supplier documentation;
- distinguishing rinse-off products from leave-on products;
- verifying the concentration of each individual substance;
- assessing whether reformulation is required;
- updating the PIF and CPSR where the formula is modified;
- reviewing labelling and CPNP notification where relevant.
Formula Review and Regulatory Adaptation
Regulation (EU) 2024/1328 is a significant regulatory update for companies using cyclic silicones in cosmetic products.
In practical terms, searching for the INCI names Cyclopentasiloxane, Cyclohexasiloxane and Cyclomethicone helps identify products that may be affected by the new requirements.
A timely review of formulations and supplier documentation allows companies to plan any necessary adaptations and ensure that cosmetic products remain compliant with the applicable European legislation.
Main source: Commission Regulation (EU) 2024/1328 of 16 May 2024 amending Annex XVII to Regulation (EC) No 1907/2006 (REACH) as regards D4, D5 and D6.