What it is
Carboxydecyl trisiloxane is a short silicone (trisiloxane) carrying a carboxylic acid functional group on a decyl chain, which gives it affinity for both pigment surfaces and the silicone phase of a formula. This makes it useful as a wetting and dispersing aid for inorganic UV filters and pigments, helping them spread uniformly and reducing a chalky appearance. It also lends a light, smooth silicone feel.
Safety & warnings
As a silicone-based dispersing agent used at modest levels, it is generally well tolerated and is not a recognized fragrance allergen.
Origin & sourcing
It is a synthetic organosilicon compound manufactured by functionalizing a siloxane backbone.
Questions everyone asks
What does carboxydecyl trisiloxane do in a sunscreen?
It helps wet and disperse mineral UV filters and pigments so they spread evenly, which improves application and reduces a chalky or uneven look.
Is it a silicone?
Yes, it is a short silicone (trisiloxane) modified with a carboxylic acid group, which gives it the ability to bind to pigment surfaces while keeping a light silicone feel.