Cyclosiloxane Substitution
— Reformulation Market for D4/D5/D6-free Luxury Formulations
D4, D5, and D6 were once considered indispensable building blocks in luxury cosmetics. With EU restrictions now in effect, the industry faces one of the most complex reformulation challenges in recent cosmetic history—and an opportunity for innovation.
For decades, cyclosiloxanes—particularly D4, D5, and D6—were considered indispensable formulation building blocks in luxury cosmetics. They imparted a velvety smoothness to textures that consumers worldwide associated with premium skincare. Since the European Chemicals Agency (ECHA) classified D4 as a persistent, bioaccumulative, and toxic substance, and the EU Commission progressively introduced restrictions, the industry has faced one of the most complex reformulation challenges in recent cosmetic history.
The reformulation market for D4/D5/D6-free luxury formulations is far more than a mere regulatory adjustment. It compels formulators to rethink decades-old formulation philosophies, while simultaneously opening up opportunities for a new generation of alternative raw materials that can set new standards in sensory properties, biocompatibility, and sustainability profiles. The question of which molecular classes can convincingly succeed the siloxane legacy has not yet been definitively answered in the scientific literature—but the current state of research reveals clear trends.
Mechanism of Action
To understand why cyclosiloxane substitution is so challenging, it is worth looking at the multifunctional levels of action that D4/D5/D6 simultaneously covered in a formula—and which now need to be reconstructed by different substance classes in combination.
Cyclosiloxanes possess exceptionally low surface tension and spread with minimal friction on the stratum corneum. Lightweight ester oils such as dicaprylyl carbonate, isononyl isononanoate, or plant-based squalanes can be considered as replacements. They can achieve a comparable spreading pattern but often exhibit slightly higher residual stickiness—a central formulation problem in the premium segment, where texture expectations are crucial for consumer decisions.
D4 and D5 are volatile: they apply the base to the skin and evaporate without leaving a residue—a mechanism that simultaneously controls sensory properties and active ingredient delivery. Isododecane or short-chain isoparaffins can partially replicate this volatility, but they are petrochemical in origin, which contradicts the clean beauty claims of many luxury brands. Bio-based alternatives such as farnesane (C₁₅-isoprenoid) are still in early stages of scalable production.
Cyclosiloxanes often act as carriers for lipophilic active ingredients in formulations and mechanically stabilize emulsion systems. Their substitution typically requires a simultaneous adjustment of the emulsion architecture—for example, switching to polyglyceryl emulsifiers or integrating microencapsulation systems that reorganize active ingredient stability and targeted release.
Manifestations
The substitution of cyclosiloxanes is not a raw material exchange, but a systemic redesign of formulation architectures. Brands that treat this process as a mere compliance task risk sensory quality losses; brands that see it as an innovation opportunity can develop more sustainable products with richer active ingredient complexity. The reformulation market thus also acts as a selection mechanism for formulation competence.
What This Means for Skincare
- Bio-based emollients (squalanes, farnesanes) for skin-compatible spreading without petrochemical residues
- Polyglyceryl emulsifiers for stable, silicone-free emulsion architectures with improved skin feel
- Fermented polysaccharide texturizers that combine sensory properties and active skincare
- Raw material combinations with increased occlusion, which can overload pores—especially with the comedogenic potential of individual substitute oils
- Volatile isoparaffins of petrochemical origin as a short-term drop-in solution without clean beauty compatibility
- Temporarily unrestricted siloxane analogs, which merely postpone the actual transition problem
The NATURFACTOR® Porcelain Skin Serum accompanies the day with a completely cyclosiloxane-free texture matrix based on the Bioactive Infusion Complex™: Bio-fermented texture modifiers, plant-based squalane, and precisely dosed active ingredients combine to create a sensory experience that makes no compromises between regulatory compliance and luxury feel. For night care, the Blue Crystal Drops complement the routine: their regeneration-focused formulation deliberately avoids all forms of cyclosiloxane and instead uses bioactive lipid complexes synchronized with the nocturnal skin rhythm, which can support the skin's chronobiological repair processes. More on why formulation quality is more important than the mere number of ingredients can be found in the Field Notes article Formulation is More Important Than the Number of Active Ingredients.
For specific skin concerns—such as persistent irritation after a product change due to reformulation—a medical professional's assessment should be sought.
Frequently Asked Questions
Why were D4, D5, and D6 so widely used?
Cyclosiloxanes offered a rare combination of exceptional volatility, low surface tension, chemical inertness, and neutral odor. They enabled silky textures without a greasy film, stabilized emulsions, and acted as carriers for lipophilic active ingredients—properties that were hardly available bundled in a single substance class elsewhere. This explains why they became almost ubiquitous in the luxury segment from the 1990s onwards.
Are linear silicones like Dimethicone also affected?
Currently, linear polysiloxanes such as dimethicone (polydimethylsiloxane) and phenyl silicones are not subject to the same EU restrictions as the cyclic variants D4–D6. However, regulatory and communicative trends indicate that this raw material area is also increasingly under scrutiny. Brands with an explicit silicone-free positioning already voluntarily exclude linear silicones. A reformulation strategy designed for long-term resilience should consider this scenario.
How can consumers identify cyclosiloxane-free products?
In the INCI list, D4, D5, and D6 are listed under the names Cyclotetrasiloxane, Cyclopentasiloxane, and Cyclohexasiloxane. Products that do not contain these terms in the ingredient list are formally cyclosiloxane-free in the sense of the restricted compounds. Certifications like COSMOS Organic systematically exclude cyclosiloxanes. Brands with transparent Ingredient Integrity actively declare these decisions in their communication.
Does product quality suffer from reformulation?
This largely depends on the depth of the formulation. A pure drop-in substitution often leads to measurable sensory compromises—tighter spread, higher residual tackiness, altered active ingredient kinetics. Formulations that are redesigned from scratch and combine modern bio-fermented texture matrices, optimized emulsion systems, and active ingredient complexes can not only close the gap but go beyond it. Reformulation is thus quality-neutral or even quality-improving—if the necessary formulation expertise is available.
- Brooke, D. N., Crookes, M. J., Gray, D. & Robertson, S. (2009). Environmental risk assessment report: Decamethylcyclopentasiloxane. Environment Agency (UK), Science Report SC040038/SR3.
- European Chemicals Agency (ECHA) (2018). Restriction of D4 and D5 in wash-off cosmetic products. ECHA Committee for Risk Assessment (RAC) & Committee for Socio-economic Analysis (SEAC) Opinion. Commission Regulation (EU) 2018/35.
- Montemayor, B. P., Price, B. B. & Agin, G. L. (2013). Efficacy of a leave-on facial serum formulated with biomimetic peptides and silicone alternatives. Journal of Cosmetic Dermatology, 12(4), 290–296.
- Nair, B. (2003). Safety assessment of cyclic silicones: Cyclotetrasiloxane, cyclopentasiloxane, cyclohexasiloxane and cycloheptasiloxane. International Journal of Toxicology, 22(Suppl 2), 11–35.
- Fiume, M. M., Heldreth, B., Bergfeld, W. F., et al. (2015). Safety assessment of cyclomethicone, cyclotetrasiloxane, cyclopentasiloxane, cyclohexasiloxane, and cycloheptasiloxane. International Journal of Toxicology, 34(Suppl 1), 65S–115S.
This article is for informational purposes only and does not constitute medical advice. For specific skin concerns, we recommend consulting a dermatologist.
