Siloxanes (Cyclic Silicones).
Also known as: cyclotetrasiloxane (D4), cyclopentasiloxane (D5), cyclohexasiloxane (D6), cyclomethicone
A group of cyclic silicone compounds used in cosmetics and skincare for their silky, smooth texture and ability to evaporate quickly. D4 in particular is a known endocrine disruptor, and all three (D4, D5, D6) are persistent environmental pollutants that bioaccumulate in aquatic ecosystems.
By the numbers.
1 = low concern, 10 = avoid.
Risk by usage.
How risk shifts depending on how often you use products with Siloxanes (Cyclic Silicones).
Low systemic concern from occasional use in leave-on products.
Daily use increases cumulative endocrine disruption risk from D4 and environmental contamination.
Significant concern for reproductive health and environmental impact. Choose siloxane-free products.
What the research says.
D4 (cyclotetrasiloxane) is a known endocrine disruptor that impairs fertility in animal studies.
European Chemicals Agency (ECHA) — D4 classified as toxic to reproduction
D4 and D5 are persistent, bioaccumulative, and toxic (PBT) in aquatic environments.
Environment Canada — D4 and D5 assessment
D5 has been shown to cause uterine tumors in animal studies at high exposure levels.
Toxicological Sciences, 2007
Global status.
How siloxanes (cyclic silicones) is regulated in cosmetics around the world.
57% of countries with data ban or restrict this ingredient
Details
D4 and D5 banned in wash-off products >0.1% since 2020; D4 restricted in leave-on >0.1% since 2023.
Details
D4/D5 restricted in wash-off at >0.1%, mirroring pre-Brexit EU rules.
Details
D4 banned where >0.1% in wash-off; D5 has environmental restrictions.
Details
D4 restricted in wash-off; D5 under review.
The reason brands include it.
Create a lightweight, silky feel that evaporates without residue. Used as a carrier fluid for active ingredients, a hair conditioning agent, and a skin-smoothing emollient.
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products in our database
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brands use it
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product categories
Better alternatives exist. Brands choose siloxanes (cyclic silicones) because it’s cheap and effective, but safer options like squalane, jojoba oil, caprylic/capric triglyceride deliver similar results without the health concerns.
Siloxanes (Cyclic Silicones) in product types.
Click a category to see every product containing siloxanes (cyclic silicones).
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What to use instead.
What Numbrrrz uses instead
Numbrrrz achieves a silky texture with Organic Jojoba Oil — a natural liquid wax ester that provides the same smooth feel as silicones without endocrine disruption or environmental persistence.