Bisoctrizole (Tinosorb M) is a hybrid type sun blocking agent acting as both chemical and physical sunscreen. Bisoctrizole is a hybrid UV absorber, the only organic UV filter produced and microfine organic particles (< 200 nm), like microfine zinc oxide and titanium dioxide. Where other organic UV absorbers need to be dissolved in either the oil or water phase, bisoctrizole dissolves poorly in both. It covers both UVA and UVB range. Furthermore, it does not degrade under sunlight and is not significantly absorbed into the skin. It appear highly compatible with many other common sun blocking agents. Overall, it appears to have a good safety profile, even though current safety data are insufficient and long-term human safety studies are lacking. Unlike some other organic sunscreen actives, it shows no estrogenic effects in vitro. Bisoctrizole is not approved by the U.S. Food and Drug Administration (FDA), but is approved in the EU and other parts of the world. Bisoctrizole is highly stable and also has a stabilizing effect on other UV absorbers, particularly the UVB blocker octyl methoxycinnamate (octinoxate). Bisoctrizole appears to be relatively non-toxic and rarely causes skin irritation. As with many synthetic chemicals, it is unclear whether bisoctrizole may produce low-level skin damage or systemic effects with long-term use. Considering that bisoctrizole is stable, poorly soluble and minimally absorbed by the skin, the risks appear to be low. Still, more research is on bisoctrizole safety is needed.