Cyclopentasiloxane: What It Is and Why It's Used

Origin

Cyclopentasiloxane (commonly called D5) is a cyclic silicone — a silicon-oxygen ring compound with five repeat units. It was developed as part of the broader silicone product range initially commercialised by Dow Corning in the mid-20th century, primarily for industrial applications before cosmetic uses were identified. Regulatory review of its environmental persistence has been ongoing since the 2010s.

Why It's Used

D5 is a light, volatile silicone that evaporates after application, leaving behind a dry, silky feel. In makeup formulations it acts as a carrier solvent — spreading pigments and actives evenly across the skin — and as a skin-conditioning agent that temporarily improves texture and appearance. Its volatility means it contributes no lasting residue.

Elsewhere

D5 and related cyclic silicones are used in industrial lubricants, mould-release agents, and as processing fluids in semiconductor manufacturing. Its environmental persistence in aquatic systems has led to regulatory restrictions on its use in wash-off cosmetics in several jurisdictions.

What the Framework Sees

Question 3, directly.

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