At a glance
| Chemical family | A cyclic volatile methylsiloxane (cVMS) — a low-molecular-weight silicone fluid; filed here as a volatile organic compound because its bedroom-relevant behaviour is airborne |
| CAS number | 541-02-6 (EC 208-764-9) |
| Classification | Not a carcinogen; low human-health concern. EU-classified very persistent & very bioaccumulative (vPvB) — an environmental classification; restricted in cosmetics on ecological, not consumer-safety, grounds |
| Where you encounter it | Antiperspirants/deodorants, hair serums and styling products, primers, foundations, sunscreens and skin lotions, as a carrier/emollient |
| Sleep micro-environment relevance | Evaporates off skin and hair into bedroom air — the dominant indoor-air siloxane; you inhale what lifted off you and your partner after the evening routine |
| Activated carbon capture | Plausibly relevant for the air phase, but ventilation and lighter use of silicone-heavy products are the simpler levers |
What it is
D5 is a silicone — specifically a cyclic volatile methylsiloxane, a small ring of alternating silicon and oxygen atoms wearing methyl groups. That structure gives it a prized set of properties in cosmetics: it spreads thinly, feels silky and dry rather than greasy, carries active ingredients evenly, and then evaporates without residue. Peer-reviewed — Dekant et al. 2016 Those qualities have made it one of the highest-volume personal-care ingredients in the world, present across antiperspirants, hair products, primers, foundations and lotions.
The single most important fact about D5 for a bedroom atlas is the last of those properties: it is volatile. It does not stay where you put it.
How it relates to the bedroom
The compound that goes into the air, not the sheets
Most of the personal-care entries in this Atlas — the parabens, the synthetic musks like galaxolide, oxybenzone — reach your bed by lingering on skin and transferring onto fabric. D5 inverts that. It lifts off your skin and hair as a vapour within minutes of application, which is why it is filed here as a volatile organic compound rather than a personal-care residue. Inferred — family assignment reflects D5's airborne behaviour rather than its product origin Measurement studies bear this out at scale: D5 is the most abundant cyclic siloxane found in indoor air, and in urban areas its mass emission rate from personal-care-product use is comparable to that of benzene from motor-vehicle traffic, peaking in the morning after people get ready and decaying over the following hours. Peer-reviewed — Coggon et al. 2018
In the bedroom, then, the exposure is inhalation — the D5 that evaporated off you, and off anyone sharing the room, hanging in the air you breathe overnight. Heat makes it worse in the obvious way: styling tools like straighteners and dryers, used near the bedroom, sharply increase how much D5 a hair product releases. Inferred — heated styling raises cVMS emissions; documented for hair-care use indoors
Why the human-health picture is reassuring
Given how much of it is in the air, the natural question is whether breathing D5 is harmful — and here the toxicology is relatively calming. Because D5 evaporates so readily, very little is absorbed through skin; the fraction that does enter the body is cleared largely by being exhaled, so it does not accumulate in people the way a persistent fat-soluble pollutant would. Peer-reviewed — Dekant et al. 2016 It is not DNA-reactive or mutagenic. The one laboratory signal worth naming honestly is a small increase in uterine tumours seen in female rats at the highest dose of a two-year inhalation study — but mechanistic work attributes that to a rat-specific hormonal pathway (an effect on dopamine signalling and the oestrus cycle), not to direct genotoxicity or oestrogen-receptor binding, and it is not considered to translate cleanly to humans. Peer-reviewed — Dekant et al. 2016 A contested strand of laboratory research has raised endocrine and breast-cell questions about siloxanes, but the weight-of-evidence reviews did not find human-health endpoints to be the deciding factor. Speculation — endocrine relevance to humans is unresolved
Restricted for the planet, not the person
So why is D5 regulated at all? Because of what it does after it goes down the drain. The EU has classified D5 as very persistent and very bioaccumulative (vPvB): it breaks down extremely slowly in water and sediment and concentrates in aquatic organisms. Identifying cosmetics as the main route by which D5 reaches the environment, the EU prohibited it above 0.1% in wash-off cosmetic products from 31 January 2020. Regulatory — EU Commission Regulation 2018/35, REACH Annex XVII entry 70 That 0.1% limit was subsequently extended to leave-on cosmetics as well, taking effect in 2026. Industry — regulatory trade press reporting the 2024 REACH amendment extending the limit to leave-on products The logic is worth stating plainly because it is easy to misread: this is an environmental restriction. D5 is limited because of its persistence in ecosystems, not because of a demonstrated hazard to the person wearing the product. Inferred — reading the vPvB basis of the restriction
What the research says
- D5 is the dominant indoor-air siloxane. It evaporates off skin and hair; urban emissions from personal care rival traffic benzene. Peer-reviewed — Coggon et al. 2018
- Human uptake is low and self-clearing. Little is absorbed; what is gets exhaled; mammalian bioaccumulation is unlikely. Peer-reviewed — Dekant et al. 2016
- Not mutagenic; the rat uterine-tumour signal is mechanism-specific. A non-genotoxic, rat-specific hormonal pathway, not direct genotoxicity. Peer-reviewed — Dekant et al. 2016
- The EU restriction is environmental. D5 is vPvB; capped at 0.1% in wash-off (2020) and leave-on (2026) cosmetics. Regulatory — EU Reg 2018/35
What helps reduce it
Ventilate after getting ready. D5 concentrations spike after product use and decay with air exchange; airflow is the most effective lever. Peer-reviewed — Coggon et al. 2018
Go lighter on silicone-heavy products near bedtime. Antiperspirants, hair serums and primers are the main sources; using less, or applying away from the bedroom, reduces what ends up in the air you sleep in. Inferred
Choosing D5-reduced formulations also helps the environment. The clearest reason to cut D5 is ecological — and EU reformulation is already lowering it in products. Regulatory — EU Reg 2018/35
What does NOT help
- Fearing D5 as a personal toxin. The evidence points to low human-health concern; the case against it is environmental. Treating it as a health threat misreads why it is regulated. Peer-reviewed — Dekant et al. 2016
- Laundering bedding to remove it. D5 is airborne, not a fabric residue, so washing sheets does little for it — unlike the parabens and musks. Inferred
Open research questions
- Whether chronic low-level inhalation of indoor D5 has any measurable human effect, given the rapid-clearance pharmacokinetics. Speculation
- How the contested endocrine and breast-cell laboratory findings on cyclic siloxanes should be weighed against the reassuring whole-animal and pharmacokinetic data. Speculation
Citations
- Dekant W, et al. (2016). Toxicology of decamethylcyclopentasiloxane (D5). Regulatory Toxicology and Pharmacology. Low dermal uptake (rapid evaporation); clearance by exhalation; bioaccumulation unlikely; not mutagenic; rat uterine-tumour signal via non-genotoxic, rat-specific mode of action. Via Consensus. Reference record Peer-reviewed
- Coggon M, et al. (2018). Diurnal Variability and Emission Pattern of Decamethylcyclopentasiloxane (D5) from the Application of Personal Care Products in Two North American Cities. Environmental Science & Technology. D5 the dominant urban-air cVMS; emission from personal care comparable to traffic benzene; diurnal peak after product use. Via Consensus. Reference record Peer-reviewed
- Commission Regulation (EU) 2018/35 amending Annex XVII to REACH as regards D4 and D5. Entry 70: D5 (CAS 541-02-6, EC 208-764-9) not to be placed on the market in wash-off cosmetics ≥0.1% by weight after 31 January 2020; basis is D5's vPvB identification with cosmetics the main environmental release route. The 0.1% limit was later extended to leave-on cosmetics (effective 2026). legislation.gov.uk Regulatory
Frequently asked questions
What is D5 and where does it come from?
D5 — decamethylcyclopentasiloxane — is a volatile silicone fluid (a cyclic volatile methylsiloxane, or cVMS) used as a carrier and emollient in personal-care products. It is what gives antiperspirants, hair serums, primers and lotions their silky, dry, fast-spreading feel; it carries the active ingredients on, then evaporates. It is in a large share of hair and skin products on the market.
Why is D5 in my bedroom air?
Because it evaporates. Unlike parabens or synthetic musks, which linger on skin and transfer onto bedding, D5's defining property is volatility — it lifts off your skin and hair into the air after you apply a product. It is in fact the single most abundant cyclic siloxane measured in indoor air, and in cities its emission rate from personal-care use rivals benzene from car traffic. So the bedroom exposure is inhaling the D5 that evaporated off you and anyone else in the room.
Is D5 dangerous to breathe?
The human-health picture is relatively reassuring. Dermal absorption is very low because D5 evaporates before it can soak in, and the small amount that does enter the body is cleared mostly by breathing it back out, so it does not build up in people. It is not mutagenic. The one laboratory flag — a slight rise in uterine tumours in female rats at the highest inhaled dose over two years — has been tied to a rat-specific hormonal mechanism that does not translate directly to humans. It is a low-concern compound for personal exposure.
Then why does the EU restrict it?
For the environment, not for you. D5 is classified as very persistent and very bioaccumulative (vPvB): when washed down the drain it lingers in water and sediment for years and accumulates in aquatic life. Because cosmetics are the main release route, the EU capped D5 at 0.1% in wash-off products from 2020 and extended that limit to leave-on cosmetics. This is one of the clearer cases where a chemical is restricted on ecological grounds while posing little direct risk to the person using it.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-06-27. If you find a factual error, contact us.