What it is
This ingredient is a chemically modified hydroxyethylcellulose carrying both a stearyl (fatty) group and an anionic sulfonate group. The cellulose backbone provides thickening and water-binding, while the attached fatty chain gives it surface activity that helps stabilize emulsions. In sunscreens it is used to control viscosity, support a uniform emulsion, and contribute to a smooth, even spread on the skin.
Safety & warnings
Modified celluloses of this type are large polymers that remain on the surface of the skin and are generally regarded as low-irritation and low-sensitization. It is not a recognized fragrance allergen and, although it carries a fatty substituent, the polymer is not used as an oil and is not associated with clogging pores at typical use levels.
Origin & sourcing
Semi-synthetic: built on a cellulose backbone, which is plant-derived, then chemically modified with fatty and sulfonate substituents.
Questions everyone asks
Why is this cellulose ingredient in my sunscreen?
It thickens the formula and helps keep the oil and water phases blended, which gives a stable product and a smooth application.
Is it derived from plants?
Its cellulose backbone comes from plant material, but it is then chemically modified, so it is best described as semi-synthetic.