Why cyclomethicone is being reformulated out
The pressure on D5 is environmental, not toxicological, and it has been building for years. The cyclic volatile methyl siloxanes — D4, D5 and D6 — are persistent, bioaccumulative and toxic to aquatic life with long-lasting effects, and they were identified as substances of very high concern on that basis. The regulatory sequence matters because it sets the clock on reformulation projects.
| Date | What changed | Practical effect |
|---|---|---|
| 31 January 2020 | Commission Regulation (EU) 2018/35 — D4 and D5 restricted to below 0.1% (w/w) in wash-off cosmetics removed with water | Rinse-off formulas using D5 had to be reformulated or withdrawn from the EU market |
| 17 May 2024 | Commission Regulation (EU) 2024/1328 adopted, amending entry 70 of Annex XVII to REACH | Extends the restriction to leave-on and other cosmetic categories, with a transition period |
| 6 June 2027 | Restriction applies to D4, D5 and D6 in leave-on cosmetics, and to D6 in wash-off products | Leave-on formulas — skin care, sun care, colour cosmetics, hair serums — must be below 0.1% (w/w) |
Two details are easy to miss. First, D4 is separately prohibited in cosmetic products under Annex II of Regulation (EC) No 1223/2009, which is a different legal instrument from the REACH restriction and applies without a transition period. Second, because D4 can appear as a trace constituent of D5 and D6 raw materials, formulators using the remaining cyclosiloxanes have to monitor technically unavoidable D4 content. That is an ongoing analytical burden attached to a chemistry you are trying to leave behind.
The tightening of the timeline is the argument for moving now rather than in 2027. Leave-on reformulation takes months of stability work, and a substitution project that starts late usually compresses the testing rather than the schedule.
What Dicaprylyl Ether is, in one paragraph
Dicaprylyl Ether is a symmetric dialkyl ether built from two C8 (caprylic) fatty alcohol chains, made from coconut- or palm kernel-derived feedstock. INCI name Dicaprylyl Ether, CAS 629-82-3, EC 211-112-6. It is also sold as Dioctyl Ether and referenced commercially as Cetiol® OE. It is a clear, colourless, low-viscosity, essentially odourless liquid with a fully saturated structure.
Two properties drive almost everything it does in a formula. The ether bond is chemically unreactive — it resists hydrolysis and it is not prone to oxidation the way unsaturated oils are, so the material is oxidatively stable and has no meaningful rancidity pathway. The short, saturated, branched-chain structure keeps the molecule small and low in viscosity, which is what produces the very high spreading rate and the fast, complete-looking absorption.
The substitution that works, and the one that does not
This is the core of the article. Cyclomethicone delivers two distinct things, and only one of them is replaceable by an ether.
Replaceable: the sensory result
Dicaprylyl Ether genuinely replicates the perceptual outcome that consumers associate with volatile silicones: a formula that spreads instantly, feels dry rather than oily, and leaves no visible film. This is the substitution that works, and it works well in emulsions, anhydrous products and pigment systems
Not replaceable: genuine volatility
Cyclomethicone leaves the skin by evaporating. Dicaprylyl Ether does not evaporate — it spreads and absorbs so quickly that it feels as though it has. In applications that depend on real evaporation — aerosol setting sprays, dry shampoos, some pump sprays — a non-volatile emollient cannot substitute on its own
The trade literature is explicit on this point: a volatile silicone replacement drawn from the ester/ether family is not a "volatile carrier". Volatile hydrocarbons are the chemistry class used when true evaporation is required
If your product depends on volatility, the honest answer is that Dicaprylyl Ether is not the whole solution. If your product depends on dry, fast-spreading, non-greasy sensory performance — which is most emulsions, most sun care and most colour cosmetics — it is an unusually good fit.
Property-by-property comparison
| Property | Cyclomethicone (D5) | Dicaprylyl Ether |
|---|---|---|
| Chemistry | Cyclic siloxane, fully synthetic | Symmetric C8 dialkyl ether, plant-derived feedstock |
| Volatility | Volatile — leaves the skin surface | Non-volatile — feels volatile but is not |
| EU cosmetic status | Restricted < 0.1% in rinse-off since 2020; leave-on from 6 June 2027 | Not restricted under Annex XVII entry 70 |
| Silicone content | Yes | None |
| Skin feel | Pure dry glide, powdery finish | Dry glide, silky, slightly more emollient body |
| Spreading | Very high | Very high |
| Oxidative stability | Excellent | Excellent — saturated ether bond, no rancidity pathway |
| Pigment dispersion | Moderate | Strong — particularly valued in mineral sun care and foundations |
| Claim compatibility | Incompatible with "silicone-free" and most "natural" positioning | Compatible with silicone-free and clean-beauty positioning |
| Typical use level | 5–20% depending on application | 5–30% depending on application |
Note the asymmetry in the last two rows. The claim compatibility difference is commercial rather than technical — and for brands selling into the clean-beauty segment, it is often the entire reason for the project.
Where it performs best in practice
Mineral and hybrid sun care
This is the strongest single application. Dicaprylyl Ether wets and disperses zinc oxide, titanium dioxide and iron oxides evenly through the oil phase, which directly reduces white cast and streaking — the two complaints that most often kill a mineral sunscreen in consumer testing. It is also an effective solvent and carrier for oil-soluble UV filters and oil-soluble actives. Typical oil-phase use levels run from around 10% to 25%.
Light facial and body emulsions
At 5–15% it transforms the oil phase of a lotion from heavy to featherlight and noticeably cuts the greasy after-feel of richer oils in the same formula. It is heat-stable and unreactive, so it can be added to the oil phase at any stage and does not interfere with emulsifiers, preservatives or actives.
Anhydrous and "dry-touch" products
Body oils, dry-touch sprays, cleansing oils and hair serums at 10–30%. In hair applications it provides slip and gloss without the weight and build-up associated with dimethicone, which is the specific reason it appears in silicone-free hair serums.
Colour cosmetics
Foundations, concealers and primers at 10–20%, where it acts as the carrier that keeps pigment evenly distributed and lets the product glide during application.
A substitution framework, in six steps
Diagnose which function you are replacing
Write down what the silicone is doing in the formula: spreading, volatility, pigment wetting, gloss, film formation. If volatility is on that list, plan a co-substitution with a volatile hydrocarbon rather than trying to force an ether to do a job it cannot do.
Match the use level by function, not by identity
Do not substitute 1:1 by mass reflexively. Because Dicaprylyl Ether is non-volatile, it stays in the formula where the silicone would have left. Start at the lower end of the range and build up.
Rebalance the whole oil phase
A non-volatile lightweight emollient at high loading can make a rich, butter-based formula feel oddly thin. Balance it against the heavier oils rather than simply swapping one line item.
Re-test pigment dispersion and SPF
In sun care, any change to the oil phase can shift the distribution of the UV filter system. Re-measure in-vitro SPF and, if applicable, in-vivo. Do not assume equivalence from the sensory result alone.
Run sensory panel comparison, not just bench assessment
Differences that seem negligible on the bench — absorbency speed, the tail-end feel after 10 minutes — are exactly what a trained panel registers. Compare the new formula against the incumbent side by side.
Confirm stability and colour over time
Standard accelerated conditions in the intended packaging, with an explicit colour and odour check. Ethers are oxidatively robust, but the surrounding formula may not be, and the interaction is what you are testing.
Common pitfalls
- Assuming it evaporates. It absorbs. If that assumption drives the formulation logic, the product will fail in exactly the applications where volatility was the point.
- Overloading rich formulas. At 20%+ in a heavy butter-based cream it can make the texture feel inconsistent and thin. It is a lightness tool; too much of it removes the body you were trying to keep.
- Confusing it with Dicaprylyl Carbonate. Similar name, different molecule, different bond, slightly different skin feel. Both are silicone-alternative emollients, but specify by INCI and CAS and do not treat them as interchangeable.
- Underusing it in sunscreen development. Formulators who struggle with white cast in mineral systems should test Dicaprylyl Ether early rather than as a last resort. Its spreading behaviour is the most directly useful property for that specific problem.
- Assuming "natural-derived" equals "no documentation needed". Plant-derived feedstock does not change your EU obligations. The REACH position, SDS and COA requirements are identical to any other substance.
Sourcing note for formulators
When this material moves from a bench trial to a purchase specification, three parameters do more work than any other in determining whether the substitution holds: colour (APHA), which decides whether it can go into white and light-tinted products; water content, which drifts over shelf life and affects stability; and residual C8 alcohol, which carries odour into the finished product. Purity alone is not a sufficient specification. Our procurement guide covers the specification and documentation side in detail.