Is Cyclopentasiloxane (D5) Safe? Its EU Status and What You Should Know
Is cyclopentasiloxane D5 harmful? We unpack the EU restriction on rinse-off products, what it means for consumers and what to look for when choosing cosmetics.
What is cyclopentasiloxane (D5)?
Cyclopentasiloxane, known by the abbreviation D5 (Decamethylcyclopentasiloxane), is a cyclic silicone — a substance from the organopolysiloxane family that is widely used in cosmetics. It is prized by formulators for its exceptional lightness, silky slip and rapid evaporation from the surface of skin and hair. You'll find it above all in hair serums, leave-in conditioners, styling products, and also in many foundations and BB creams.
For years D5 was considered an ingredient with a good safety profile for humans — non-irritating, non-comedogenic and chemically inert on the skin. The controversy surrounding it, however, concerns not so much its direct impact on the user's health as its effect on the aquatic environment.
Why did the EU restrict the use of D5?
In December 2020, Commission Regulation (EU) 2020/1149 came into force, amending the REACH Regulation (1907/2006). Under this regulation, D5 (along with D4 and D6) was placed on the list of substances subject to restrictions on account of its PBT properties — being Persistent, Bioaccumulative and Toxic to aquatic organisms.
The restriction applies specifically to rinse-off cosmetic products, where the concentration of D5 exceeds 0.1%. This category includes shampoos, rinse-off conditioners, shower gels and bath products. Once rinsed off, D5 ends up in wastewater, and because it is difficult to biodegrade it accumulates in the aquatic environment and in bottom sediments.
What about leave-on products?
The 2020 restriction does not apply to leave-on products — serums, creams, leave-in conditioners or foundations. That is why D5 still legally appears in these products, and its use as such is not banned.
It is worth noting, however, that the European Chemicals Agency (ECHA) monitors the substance as part of a broader strategy to restrict microplastics and persistent organic pollutants. Future regulations may also cover leave-on products — consumers and the cosmetics industry are well aware of this.
Is D5 safe for human health?
The SCCS issued an opinion (SCCS/1549/15 and updates) stating that D5, when used cosmetically at typical concentrations, poses no risk to the user's health. The substance shows low acute and chronic toxicity in mammals. Absorption through the skin is limited, and what is absorbed is metabolised and excreted.
No significant endocrine-active properties of D5 have been found in humans, although studies in rodents showed certain effects at very high inhalation doses (not relevant to typical cosmetic use). D5 is not classified as a carcinogen or a mutagen for humans.
D5 and microplastics — an important distinction
D5 is sometimes confused with microplastics, although technically it is not one — it is a liquid silicone, not a solid plastic particle. Nevertheless, the regulatory logic is similar: the concern is substances that persist in the environment, are hard to biodegrade and are potentially bioaccumulative. If you take a broader interest in persistent contaminants in cosmetics, this topic ties in with EU policy on PFAS and other substances from the PMT/PBT group.
How to spot D5 in an ingredient list — and what to do about it
On the INCI label, look for the name CYCLOPENTASILOXANE. A full list of silicones together with their characteristics is available in the PurScore ingredient encyclopaedia.
Practical tips:
- Check whether the product is rinse-off or leave-on — in the former case, D5 above 0.1% has been non-compliant with EU law since 2020.
- If you want products without D5 for environmental reasons, look for formulas with alternatives such as isopentyldiol, squalane or cetyl ethers
- In leave-on hair products D5 remains legal and common — the decision to avoid it depends on your personal environmental preferences
For a fuller picture, it's worth browsing the available lists of top-rated products, where the ingredient profile is taken into account.
Note: this article is for informational purposes only. If you have any concerns about skin reactions, consult a dermatologist.
FAQ
D5 is not completely banned. Since 2020 (Regulation EU 2020/1149) its use at concentrations above 0.1% has been prohibited in rinse-off products (shampoos, gels). In leave-on products (serums, creams) D5 is still permitted.
Yes — according to the SCCS opinion, D5 used cosmetically and externally in the usual way poses no significant risk to human health. The concerns relate mainly to its impact on the aquatic environment, not to direct toxicity for the user.
Look for the name CYCLOPENTASILOXANE. Other cyclic silicones are CYCLOHEXASILOXANE (D6) and CYCLOTETRASILOXANE (D4). You can check their profiles in the ingredient encyclopaedia on PurScore.pl.
As a class, silicones are generally safe for your health. Their main drawback is that they can weigh hair down with prolonged use without regularly using a clarifying shampoo. The D5 issue is primarily about protecting the environment, not the user's health.
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