What it is
Carboxydecyl Dimethicone is a functionalized polydimethylsiloxane in which some methyl groups are replaced by carboxydecyl side chains — a hydrocarbon residue of approximately 11 carbons terminating in a carboxylic acid group. This modification improves compatibility with aqueous and polar ingredients compared to standard dimethicone, while retaining the silky slip, low surface tension, and vapor-permeable film-forming properties characteristic of silicone polymers. In formulations it acts as an emollient and skin-conditioning agent, leaving a soft, non-greasy feel, and as a hair conditioner it reduces friction between fibers, improving combability and shine. The carboxyl groups also contribute mild substantivity, helping the ingredient deposit and adhere to hair and skin surfaces more effectively than unmodified dimethicone.
Safety & warnings
The Expert Panel for Cosmetic Ingredient Safety has concluded that dimethicone and related silicon-based polymers are safe as used in cosmetics. Carboxydecyl Dimethicone is considered non-comedogenic and has a low irritation potential, making it suitable for sensitive skin. As with other airborne silicone ingredients, inhalation risk from aerosol application is an area where data remain limited. No significant allergenicity or skin sensitization concerns have been identified for this class of ingredient.
Origin & sourcing
Carboxydecyl Dimethicone is a synthetic ingredient produced by chemical modification of polydimethylsiloxane (dimethicone). The carboxydecyl functional groups are introduced through controlled reaction of the silicone backbone, typically via hydrosilylation or co-polymerization chemistry. The base silicone raw material is derived from silicon, quartz, or related silica sources, processed industrially.
History
Carboxyl-functional silicones were developed as part of broader efforts to create reactive and substantive silicone polymers for personal care applications. Shin-Etsu Chemical and Momentive Performance Materials have commercially supplied carboxy-modified silicones (including related Bis-Carboxydecyl Dimethicone) to the cosmetics industry. The ingredient is listed in the EU CosIng cosmetic ingredient inventory and has been used in hair and skin care formulations for several decades.
Questions everyone asks
What makes Carboxydecyl Dimethicone different from regular dimethicone?
Regular dimethicone is a straight polydimethylsiloxane with methyl groups along its backbone. Carboxydecyl Dimethicone has some methyl groups replaced by carboxydecyl chains — roughly 11-carbon arms ending in a carboxylic acid.
What cosmetic products typically contain Carboxydecyl Dimethicone?
It is used in skincare creams and serums (as an emollient and film former), as well as in hair conditioners, leave-in treatments, and styling products where it helps reduce friction, improve combing ease, and add shine.
Is Carboxydecyl Dimethicone safe for sensitive skin?
Yes. It is considered non-comedogenic and has a very low irritation profile (rated 1/5 on irritancy scales). Regulatory bodies including the EU CosIng inventory list it without restrictions, and the broader class of dimethicone polymers has been assessed as safe by the Expert Panel for Cosmetic Ingr
Is Carboxydecyl Dimethicone natural or synthetic?
It is a synthetic ingredient made by chemically modifying polydimethylsiloxane. The underlying silicon is mineral-derived (from silica), but the finished ingredient is produced through industrial chemical synthesis and is not considered a natural or plant-derived material.