The regulatory landscape for cyclic silicones is changing how cosmetic manufacturers approach ingredient selection and formulation development. Restrictions affecting Cyclotetrasiloxane (D4), Cyclopentasiloxane (D5), and Cyclohexasiloxane (D6) have expanded under the European Union’s REACH regulation. These developments have increased demand for alternative technologies capable of maintaining spreading, lubrication, and sensory performance without relying on restricted cyclic siloxanes.
For cosmetic chemists, the challenge extends beyond identifying suitable replacement ingredients. Regulatory compliance requires an understanding of concentration limits, implementation dates, product classifications, and the potential presence of cyclic siloxane residues in supplied raw materials. Reformulation must also address the functional properties that these ingredients contribute to skin care, hair care, and color cosmetic products.
Commission Regulation (EU) 2024/1328 establishes a broader restriction framework for D4, D5, and D6, with a major implementation deadline for cosmetics on June 6, 2027. Understanding the regulation allows R&D, regulatory, and procurement teams to plan ingredient qualification and formulation development before the applicable requirements take effect.
Understanding D4, D5 and D6 in Cosmetic Formulations
D4, D5, and D6 belong to a family of cyclic methylsiloxanes characterized by ring structures containing alternating silicon and oxygen atoms. Although these substances share structural similarities, differences in molecular size, volatility, and physical properties influence their formulation behavior.
D4, or Octamethylcyclotetrasiloxane, contains four siloxane units within its cyclic structure. D5, known as Decamethylcyclopentasiloxane, contains five units, while D6, or Dodecamethylcyclohexasiloxane, contains six.
These materials have historically served different roles in cosmetic and industrial applications. D5 has been particularly relevant in personal care because of its low-viscosity spreading and volatile sensory properties. D6 offers related characteristics but exhibits different evaporation behavior due to its molecular structure.
Why Cyclic Silicones Are Used in Cosmetics
Volatile cyclic silicones can improve initial spreading, reduce friction during application, and contribute to lightweight sensory characteristics. Their volatility allows them to function as temporary carriers for other cosmetic ingredients.
In skin care, these properties can support smooth application and a relatively dry residual finish. Hair care formulations may use volatile silicone carriers to help distribute conditioning ingredients, while color cosmetics can incorporate them into systems involving pigments, elastomers, resins, and film-forming technologies.
The removal of these materials can therefore affect more than the sensory profile. Depending on the formulation, alternative carrier selection may influence viscosity, dispersion stability, ingredient compatibility, and the formation of the residual film.
This functional complexity explains why replacement strategies require a more detailed approach than simply substituting one lightweight emollient for another.
Why the European Union Is Restricting D4, D5 and D6
European regulatory assessments have identified environmental concerns associated with the persistence and bioaccumulation characteristics of specific cyclic siloxanes. These characteristics influence how substances behave following release and contribute to the assessment of potential long-term environmental effects.
In June 2018, the European Chemicals Agency’s Member State Committee identified D4, D5, and D6 as substances of very high concern because of their very persistent and very bioaccumulative properties.
D4 also met the criteria for persistent, bioaccumulative, and toxic properties. The assessments identified additional PBT concerns for D5 and D6 when they contain D4 at concentrations of at least 0.1% by weight.
These distinctions are important because regulatory classifications relate to specific substances and defined criteria. They should not automatically extend to every silicone polymer, linear Dimethicone grade, or silicone-derived ingredient.
Environmental Persistence and Exposure
Cyclic siloxanes can enter environmental compartments through manufacturing, industrial activities, and consumer product use. Their distribution depends on properties such as volatility, solubility, partitioning behavior, and environmental conditions.
In rinse-off cosmetics, ingredients may enter wastewater treatment systems directly during use. Leave-on products follow different release pathways, including evaporation, transfer to other surfaces, and eventual removal during washing.
Regulatory assessments consider these pathways alongside persistence, bioaccumulation, and other relevant environmental properties.
The expanded EU restriction reflects concerns extending beyond the original rinse-off cosmetic applications. For formulators, this creates a need to evaluate the regulatory status of the exact silicone substances present in the finished product rather than rely on broad descriptions of silicone chemistry.
EU Restriction Timeline: What Changes in 2026 and 2027?
Commission Regulation (EU) 2024/1328, published in May 2024, amended Annex XVII of REACH and expanded entry 70 concerning D4, D5, and D6.
The regulation establishes restrictions on placing these substances on the market, whether individually, as constituents of other substances, or within mixtures, subject to specified concentration limits, implementation dates, and derogations.
The general concentration threshold is 0.1% by weight for each of the three substances.
January 31, 2020: Earlier Wash-Off Restrictions
Restrictions on D4 and D5 in wash-off cosmetic products have applied since January 31, 2020.
Under this framework, cosmetic products that consumers normally wash off with water after application cannot be placed on the EU market when they contain either restricted substance at or above the applicable 0.1% threshold.
This earlier restriction established the foundation for the broader measures that followed.
June 6, 2026: Expanded Restrictions Take Effect
The expanded REACH restriction reached a major implementation date on June 6, 2026.
The general restrictions apply to D4, D5, and D6 as substances, constituents, or components of mixtures at concentrations equal to or greater than 0.1% by weight, subject to the regulation’s application-specific derogations.
For cosmetic products, this includes the expansion to D6 in wash-off applications. Other cosmetic categories have a separate implementation date under the regulation.
This distinction matters for regulatory planning because the June 2026 deadline does not mean that every cosmetic category became subject to the same restriction on that date.
June 6, 2027: Broader Cosmetic Restrictions
June 6, 2027, represents the next major deadline for cosmetic manufacturers.
Under the regulation’s specific cosmetics derogation, the expanded restrictions apply from this date to cosmetic products other than those already covered by the earlier D4 and D5 wash-off provision.
This includes leave-on cosmetic applications, making the deadline relevant to many skin care, hair care, and color cosmetic formulations intended for the European market.
Manufacturers should review finished-product concentrations, supplied raw material compositions, and relevant regulatory documentation well before the deadline.
The restriction concerns placing products on the market and must be interpreted according to the complete legal text, including applicable exceptions. Companies should obtain regulatory advice where product classification, residual concentrations, or specialized uses create uncertainty.
What the 0.1% Concentration Limit Means for Formulators
The concentration threshold is a critical part of the regulation. It applies to D4, D5, and D6 individually rather than simply establishing a combined total for all cyclic siloxanes.
For cosmetic R&D teams, this creates several practical considerations.
A formulation may contain one of the substances as an intentionally added ingredient. Alternatively, cyclic siloxanes may occur as residual constituents within certain supplied silicone materials. The distinction between intentional use and residual presence does not eliminate the need to evaluate the applicable legal requirements.
Suppliers should provide sufficient information to support concentration assessments when their ingredients may introduce restricted cyclic siloxanes into the finished product.
The regulation also contains specific derogations covering certain industrial uses, medical applications, and residual concentrations in defined categories. These provisions should not be treated as general exemptions for conventional cosmetic products.
For accurate compliance assessment, regulatory teams should identify the individual substance, its concentration, the intended use, and the relevant implementation date.
Formulation Challenges When Replacing D4, D5 and D6
Removing volatile cyclic silicones may influence several characteristics of the finished formulation. The effects depend on the original silicone, its concentration, and the surrounding ingredient system.
In lightweight skin care products, D5 may contribute rapid spreading and a smooth application profile. Replacing it with a less volatile emollient can alter the residual feel, even when initial spreading remains comparable.
Hair care formulations introduce additional requirements. Cyclic silicone carriers may influence the distribution of conditioning ingredients and the development of softness, shine, or lubrication during application.
Color cosmetics can present greater complexity when volatile silicones function as carriers within systems containing pigments, silicone elastomers, resins, or other film-forming components. Replacing the carrier may change dispersion behavior, application uniformity, or wear characteristics.
These differences make it essential to define the original ingredient’s role before selecting an alternative.
Volatility, Spreading and Dry-Down
Volatility represents one of the defining characteristics of D5 and D6. During application, these materials can spread across the surface and subsequently evaporate, changing the composition of the remaining film.
Some natural-origin hydrocarbons and engineered ester systems provide favorable spreading characteristics. However, their evaporation behavior varies considerably.
A replacement may reproduce initial slip but leave a more substantial residual layer. Another may provide a lightweight finish through its viscosity and interfacial properties rather than through the same evaporation mechanism.
Formulators should therefore evaluate evaporation behavior, spreading, lubrication, and residual sensory performance as separate but related parameters.
Compatibility With Pigments and Functional Ingredients
Volatile silicone replacement can also affect ingredient compatibility.
Differences in polarity and solvent characteristics may influence pigment wetting, film-former behavior, or interactions with other oil-phase components.
For example, a hydrocarbon-based alternative may support a relatively nonpolar formulation environment, while a selected ester can offer different solvent characteristics for organic ingredients.
The appropriate choice depends on the complete formulation. A material that performs well in a facial serum may not provide equivalent performance in a pigment-rich foundation or structured hair treatment.
Compatibility screening should therefore begin during initial ingredient selection rather than after the sensory profile has been finalized.
Selecting Alternatives to D5 and D6
Several non-siloxane ingredient technologies can support reformulation strategies involving volatile cyclic silicones.
These include lightweight hydrocarbons, bio-based alkanes, selected esters, and blended sensory systems. Each family provides different combinations of spreading, lubrication, volatility, and residual characteristics.
| Replacement approach | Potential formulation contribution | Important evaluation |
|---|---|---|
| Lightweight hydrocarbons | Spreading and lightweight sensory | Volatility, residual feel, compatibility |
| Bio-based alkanes | Slip and sensory modification | Molecular structure, evaporation, renewable-content documentation |
| Engineered esters | Lubrication and solvent characteristics | Polarity, spreading, residual film |
| Blended emollient systems | Balanced sensory performance | Component compatibility and stability |
| Structured sensory systems | Cushion and texture modification | Rheology, application, residual behavior |
These technologies represent potential formulation approaches rather than universal drop-in replacements.
Research into bio-based alternatives to volatile silicones has demonstrated that molecular structure strongly influences physicochemical and functional performance. Selecting an appropriate replacement therefore requires comparison with the actual silicone reference used in the original formulation.
In many applications, a combination of materials may achieve a more suitable sensory profile than a single ingredient.
Developing a Regulatory Reformulation Strategy
A structured reformulation program helps cosmetic manufacturers address regulatory requirements while maintaining technical performance.
The first step is to identify products containing D4, D5, or D6 and determine the relevant regulatory deadlines. This review should include intentionally added ingredients and any relevant cyclic siloxane residues introduced through supplied materials.
The next step involves defining the functional contribution of each substance. If D5 serves primarily as a volatile sensory carrier, alternative screening should focus on spreading, evaporation, and residual characteristics. Where the original silicone also supports dispersion or film formation, the evaluation must include those properties.
Once candidate technologies have been identified, formulators can compare their performance using appropriate instrumental and sensory methods.
Stability and Technical Qualification
Alternative ingredients should undergo compatibility and stability evaluation within the complete formulation.
Relevant testing may include viscosity measurements, evaporation profiling, pigment dispersion analysis, sensory assessment, and storage stability.
The specific test program depends on product type. For example, sunscreen formulations may require additional verification of UV-filter behavior and photoprotective performance after changes to the oil phase.
Commercial qualification also requires attention to manufacturing reproducibility. Changes in processing conditions can affect texture, dispersion, and stability, particularly when replacing multifunctional silicone carriers with blended systems.
Early technical evaluation allows formulators to identify performance differences and adjust the formulation before pilot-scale or commercial production.
Supplier Documentation and Regulatory Readiness
The expanded restrictions make clear ingredient documentation particularly important for suppliers and cosmetic manufacturers.
Companies developing products for the European market should maintain records that establish the regulatory status and composition of materials relevant to the restriction.
Important information can include ingredient identification, available compositional specifications, regulatory statements, and analytical data supporting relevant concentration assessments.
For alternative materials, documentation may also include technical specifications, safety information, recommended use levels, formulation guidance, and available environmental data.
However, silicone-free origin does not automatically establish compliance with every applicable cosmetic regulation. Alternative ingredients must satisfy the requirements relevant to their chemistry and intended application.
Similarly, renewable sourcing and biodegradability should be evaluated independently from the absence of restricted cyclic siloxanes.
Planning Beyond the 2027 Deadline
The EU restrictions create a clear regulatory milestone, but successful reformulation also depends on long-term ingredient strategy.
Brands developing products for multiple markets may choose to harmonize formulations around common internal standards. Such decisions can simplify product portfolios, although legal requirements continue to differ between jurisdictions.
Ingredient suppliers and cosmetic R&D teams can support these efforts by developing replacement systems with suitable technical documentation and reproducible performance.
Natural-origin hydrocarbons, engineered esters, and advanced emollient technologies offer opportunities to reproduce selected sensory functions associated with volatile silicones. Their effectiveness depends on formulation context and the properties that must be maintained.
For cosmetic manufacturers, the most reliable approach is to connect regulatory planning with early technical screening, supplier qualification, and application-specific testing.
The D4, D5, and D6 restrictions should be approached as defined regulatory requirements that demand informed formulation decisions. Accurate interpretation of deadlines, concentration thresholds, and ingredient composition provides the foundation for compliance. Functional evaluation then allows formulators to select alternative technologies without sacrificing the performance expected from modern cosmetic products.
Explore Natural Silicone Replacement Technologies
Grand Ingredients offers a specialized portfolio of natural-origin silicone alternatives for skin care, hair care, and personal care formulations. The SILIKE range includes technologies developed to support selected silicone-like characteristics, including spreading, lubrication, softness, conditioning, and sensory modification.
For cosmetic R&D teams preparing for the EU restrictions on D4, D5, and D6, appropriate ingredient selection begins with understanding the original silicone’s function and the performance requirements of the finished formulation.
Explore our Natural Silicone Alternatives portfolio to identify relevant technologies and request technical specifications, supporting documentation, or samples for formulation development.
Research References
- European Commission. Commission Regulation (EU) 2024/1328 of 16 May 2024 amending Annex XVII to REACH as regards D4, D5 and D6. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32024R1328
- European Chemicals Agency (ECHA). Cyclosiloxanes: Regulatory and Environmental Assessment Information. https://echa.europa.eu/hot-topics/cyclosiloxanes
- European Commission. Commission Regulation (EU) 2018/35 restricting D4 and D5 in wash-off cosmetic products. https://eur-lex.europa.eu/eli/reg/2018/35/oj
- Goussard, V., Aubry, J.-M., & Nardello-Rataj, V. (2022). Bio-based alternatives to volatile silicones: Relationships between chemical structure, physicochemical properties and functional performances. Advances in Colloid and Interface Science, 304, 102679. https://doi.org/10.1016/j.cis.2022.102679
