Cyclomethicone

Cyclomethicone is a volatile silicone used as a slip/solvent vehicle (often a major phase in serums/primers and hair products), and it is generally non-reactive with very low rates of irritation in patch-testing and clinical use. While it is not truly inert for every patient—rare stinging can occur on severely compromised or fissured skin and ocular exposure can be uncomfortable—its irritation potential at typical cosmetic concentrations is exceptionally low. Given sensitive-skin safety and the need to avoid underestimating risk, it fits best as exceptionally gentle rather than completely inert. Safety Notes: In commercial skincare, cyclomethicone is often used at very low levels (~0.1–1%) as a slip/feel and spreadability modifier in emulsions (creams/lotions, sunscreens, and some cleansers/rinse-off products). Mid-range use is common in primers, silicone-rich serums, and makeup-adjacent skincare (typically ~5–30%). The highest consumer-available levels are seen in anhydrous silicone fluids/“dry oil” body products and silicone-based primers where cyclomethicone can be the primary carrier (often ~50–90% depending on blend with other volatile/non-volatile silicones); these are OTC and not prescription-only.