What it is
Stearoxy dimethicone is a dimethicone (polydimethylsiloxane) backbone bearing a stearyloxy (long fatty-chain) substituent, combining the slip of silicone with the waxy character of a C18 group. This hybrid structure gives it semi-solid behavior that helps thicken and stabilize emulsions while leaving a smooth, conditioned skin feel. In sunscreens it can improve texture and film characteristics.
Safety & warnings
Alkyl-modified silicones such as stearoxy dimethicone are generally regarded as low-irritant and well tolerated. Like other silicones they are inert and not associated with significant sensitization at cosmetic use levels.
Origin & sourcing
Synthetic; an alkyl-modified silicone made by attaching a stearyl-derived group to a dimethicone polymer.
Questions everyone asks
What kind of ingredient is stearoxy dimethicone?
It is a silicone modified with a long fatty (stearyl) group, giving both silicone slip and a waxy, emollient quality.
Why is it used in sunscreen?
It conditions skin, improves the texture of the formula, and helps stabilize and thicken the emulsion.