Polyhydroxystearic acid is a suspending agent.
Although Polyhydroxystearic Acid is a widely used ingredient in skin care, beauty and cosmetic products, very little information is available regarding its properties. According to Skin Essentials and the Cosmetic Database, as well as various patents that include it in formulas, it is a suspending agent and emulsifier that is used to stabilize products. It is often seen in formulas that contain an SPF component, such as sunscreens.
Polyhydroxystearic acid is a commonly used dispersant for ultrafine titanium dioxide and zinc oxide. It is available from Innospec as Dispersun DSP-OL100 Sunscreen and the suppliers claim that it dramatically decreases the viscosity of dispersions at dose rates of just a few percent, allowing higher concentrations of pigment to be used, and that it significantly improves optical transparency and UV absorption.
Polyhydroxystearic Acid is rated as a low hazard ingredient by the Cosmetics Database, and is only known to cause bioaccumlation, therefore limiting its use in Canada. Otherwise, the only concern found by the Cosmetics Database was a lack of data; no studies were found that noted negative side effects or safety measures concerning Polyhydroxystearic Acid as an ingredient in cosmetics and skin care products.