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Ingredient dossier · No. 020

Cyclic Siloxanes (D4/D5)

Also: cyclopentasiloxane · cyclotetrasiloxane · D4 · D5 · cyclic silicones · dimethicone derivatives


AvoidEU classifies D4 as a reproductive toxicant and restricts both D4 and D5 in rinse-off cosmetics.


01 · Hormonal impact

Testosterone & hormonal load

Evidence
ModerateAnimal studies with mechanistic evidence

D4 (cyclotetrasiloxane) is classified as a reproductive toxicant (CMR Category 2) by the EU following animal studies showing uterine tumors and adverse reproductive outcomes. D5 (cyclopentasiloxane) shows estrogenic activity in cell studies and is highly persistent in the environment. Both are restricted in rinse-off cosmetics in the EU at concentrations above 0.1%. They are used extensively as silky-feel agents in hair and grooming products.


02 · Where it appears

Found in.

01Hair styling products (silky feel)
02Conditioner
03Deodorant and antiperspirant
04Shaving products
05Moisturizer

03 · The regulators

Two jurisdictions, two different verdicts.

European Union

D4 and D5 restricted to ≤0.1% in rinse-off cosmetics under EU Regulation 2018/35. D4 classified as reproductive toxicant (CMR 2). Both listed as SVHCs by ECHA.

United States · FDA

No current restriction on D4 or D5 in cosmetics in the US.


04 · Sources

The receipts.

  1. [01]
    EU Regulation 2018/35 — D4 and D5 restriction in rinse-off cosmetics
    eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32018R0035
  2. [02]
    SCCS/1549/15 — Safety assessment of D4 and D5
    ec.europa.eu/health/scientific_committees/consumer_safety/docs/sccs_o_195.pdf
  3. [03]
    ECHA — Cyclopentasiloxane SVHC listing
    echa.europa.eu/substance-information/-/substanceinfo/100.039.913
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