Short answer: octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) are the volatile silicones that give a formula its dry, silky, fast-finishing feel — and the EU restriction on them now reaches leave-on products on a published horizon. Replacement is possible, but the substitution is a sensory and packaging project, not an ingredient swap.
Nothing in a skincare or hair-care range works harder and gets less credit than the volatile cyclics. They are why a serum disappears into skin instead of sitting on it, why a foundation spreads before it sets, and why a hair oil gives slip without weight. They are also volatile, persistent and bioaccumulative enough that EU regulators decided the wash-off and the worn-off fraction were not adequately controlled — and once a substance is classified that way, the restriction arrives in tranches: rinse-off first, then everything you leave on the skin.
That second tranche is the one now on the calendar. This article covers what each cyclic does, where it hides in a formula, what can replace it, and the failure modes that decide whether a substitution survives the first hot summer.
Why the cyclics were singled out
D4, D5 and D6 are small, cyclic, fully volatile siloxanes. That combination is what makes them useful and what makes them a regulatory target at the same time.
- They are persistent and bioaccumulative. D4 in particular has been assessed as persistent, bioaccumulative and toxic, and D5 and D6 have been assessed as very persistent and very bioaccumulative. Substances with that profile do not need a demonstrated harm in cosmetic use to attract restriction; the profile itself is the trigger.
- They are volatile, so they do not stay in the product. A volatile carrier evaporates from skin or hair and becomes an air emission, which is a different regulatory question from a chemical rinsed into water. That is why the wash-off restriction came first and the leave-on one followed.
- They are not chemically interchangeable with the linear silicones. Dimethicone is a linear polymer and a different substance with a different assessment. "Silicone-free" and "cyclic-free" are not the same claim, and a brand that conflates them usually ends up making a claim it cannot document.
The practical signal for formulators is simple: this is an environmental-profile restriction, not a question about safety in use, and the phase-in is by format because reformulation difficulty differs enormously between a shampoo and a long-wear foundation.
Where D4, D5 and D6 actually sit in a formula
The table below is the map most brands need before they brief anything. The right-hand column is the part that gets underestimated: every one of these functions is load-bearing.
| Cyclic | What it does in the formula | Where it turns up | What changes when it goes |
|---|---|---|---|
| D4 | Volatile carrier and diluent, keeps the formula mobile during application | Antiperspirants, hair sprays, light skin fluids | Higher tack during rub-in; slower, stickier dry-down |
| D5 | The sensory workhorse — dry, silky feel, fast spread, quick evaporation | Foundations, primers, hair serums, deodorants, sun fluids | Loss of slip; product feels heavier and takes longer to set; sun fluids drag and leave a visible film |
| D6 | Higher-boiling cyclic, extends play time and shine, resists quick evaporation | Colour cosmetics, long-wear base products, hair treatments | Shorter working time before set; shine and gloss drop off; wear time shortens |
Two patterns matter commercially. First, D5 and D6 are usually used together, so removing one without the other gives an inconsistent result — a shorter working time without recovering the slip. Second, the formats where the cyclics do most work are exactly the formats with the longest regulatory horizon, because rebuilding wear and shine without them is an engineering problem rather than a pleasant swap.
The dates
The rinse-off restriction on D4 and D5 has been in force since 2020. A later amendment to the same REACH Annex XVII entry extended the scope: D6 was brought inside the rinsed-off restriction with a transition that closed in June 2026, and leave-on cosmetic products are to be free of all three cyclics from June 2027.
Confirm the operative date against the current consolidated entry before you commit artwork — consumed dates move, transitions get extended, and a label printed against an outdated reading is a reprint.
If you are also working through the EU's other ingredient annex changes in the same cycle, the re-testing and file-update work overlaps almost entirely with what we describe in our EU Regulation 2026/909 guide. Bundle the projects; do not run them sequentially.
Substitution routes that hold up
There is no single drop-in. There are three families of replacement, and the right one depends on whether the brief prioritises dry-down, wear, shine or a natural-origin story.
- Volatile hydrocarbon carriers — materials such as low-viscosity alkanes and isoalkanes evaporate quickly and give a dry finish close to what D5 provided. They are chemically simple and widely available. Their weakness is compatibility: hydrocarbons swell and craze some plastics and can attack certain adhesives and pump components, so packaging qualification becomes mandatory rather than advisable.
- Non-volatile linear silicones and siloxane-based film formers — dimethicone and alkyl-modified linear silicones give slip and softness, and siloxane film formers contribute wear and transfer resistance in colour. These stay on the skin, which means the finish is richer and less powdery, and the claim language has to change accordingly.
- Ester and botanical routes — alkyl benzoates, plant-derived alkanes and squalane-type emollients. These support a clean-label story and often improve the skin-feel on dry skin types, but they are heavier, oxidise more readily and can drag on application. Squalane-based systems are well suited to this route; our squalane serum base is built on exactly that trade-off.
A defensible formula usually blends two of the three: a fast volatile for the dry-down, a heavier emollient for the cushion, and a film former for wear. That is also why substitution takes a cycle rather than an afternoon.
Failure modes when you swap a volatile
These are the four that show up in real projects, in the order they typically appear:
- Soaping and white residue. Volatiles leave no visible trace. Heavier replacements can leave a film that whitens when the user rubs or sweats — most visible in sun fluids and in colour products worn over a water-based serum.
- Delayed dry-down. The consumer's first judgement is how the product feels for the first ninety seconds. A substitution that adds thirty seconds to set reads as "greasy" even when the wear data is identical.
- Packaging incompatibility. Hydrocarbon carriers interact with polymer components, and the failure is often slow: a pump that stiffens after two weeks, a label that lifts, a liner that swells — a defect that appears after shipping, not during filling.
- Viscosity and phase drift over shelf life. The volatile fraction was also a diluent. Remove it and the internal phase concentration changes, which changes texture at 40°C. A formulation that behaves at 25°C in the lab can separate in a warm warehouse — the mechanisms behind that are covered in our emulsion technology explainer.
The counter-intuitive one is number two. Teams spend their time on wear testing, which is measurable, and neglect the ninety-second sensory window, which decides repurchase.
Testing before you commit
A substitution programme needs four specific tests, and skipping any one of them moves the risk to the customer:
- Accelerated and real-time stability on the new composition, at two or more temperatures, with texture measured rather than described.
- Pack compatibility — the replacement carrier in the actual pack, held at temperature, with the pump, the liner and the label all in the assembly being qualified.
- Preservative efficacy re-test, because a changed dispersed phase changes how well the system is preserved even when the preservative has not moved.
- Sensory panel against a retained Golden Sample — a physical reference of the approved colour, texture and finish, not a photograph or a memory. That retained reference is the only way to hold a sensory standard across batches and across substituent changes.
For hair-care formats that depend on the volatile for gloss and slip — treatments, serums and systems such as a glossing treatment — add combing-force and shine measurement to the panel, because the perceived difference is larger than the instrumental difference.
What this means for your brief
If you are commissioning a leave-on format now, the cheapest decision you can make is to specify the finish you want and let the base be built cyclic-free from the start, rather than shipping a formula you will rebuild within two years.
Three questions to put to any manufacturer:
- Which volatiles are in this base, at what percentage, and which format group's horizon applies?
- What is the pack compatibility evidence for the replacement carrier in the actual component, not the reference one?
- How is the sensory standard retained, and will I receive the Golden Sample reference with the batch documents?
Every order we release ships with a certificate of analysis, a stability summary and a microbiological report against the specification actually produced — the three documents that make a substitution defensible to a regulator and to a retailer's quality team.
FAQ
Q: Are cyclic silicones banned in cosmetics altogether? A: No. The restriction is phased and format-specific: D4 and D5 have been restricted in rinsed-off cosmetics since 2020, D6 was brought into the rinsed-off restriction with a transition closing in June 2026, and leave-on cosmetic products are to be free of all three from June 2027.
Q: Is a 'silicone-free' claim required once the cyclics are removed? A: No, and it can be misleading. Linear silicones such as dimethicone are different substances with different regulatory assessments, and they are not covered by this restriction. If a replacement base still contains a linear silicone, a silicone-free claim is inaccurate.
Q: What is the closest replacement for D5 in a foundation or serum? A: There is no single drop-in. Volatile hydrocarbon carriers get closest to the dry-down but require pack compatibility testing; linear silicones and siloxane film formers protect slip and wear but leave a richer finish; ester and botanical emollients support a clean-label story but feel heavier. Most workable systems blend two of the three.
Q: Why does a substituted formula fail only after shipping? A: Because two of the four common failure modes are slow. Hydrocarbon carriers can swell a liner or stiffen a pump over weeks in transit, and the loss of a volatile diluent can shift texture at warehouse temperature even when the formula behaves in a 25°C laboratory. Both are caught by pack compatibility testing and accelerated stability, not by a bench evaluation.