Chemical UVA+UVB sunscreen/sunblock - Bisoctrizole (Tinosorb M)

Generic name: Bisoctrizole; methylene bis-benzotriazolyl tetramethylbutylphenol

Brand(s): Tinosorb M

Type: Hybrid (Chemical and Physical)

Range of UV spectrum covered: UVA (both UVA-1 and UVA-2), UVB

Wavelengths covered: about 280-400 nm, which covers both UVB and UVA ranges; peak protection at 303 nm and 358 nm

Stability:
Bemotrizinol is stable when exposed to sunlight. It can also partly protect other chemical sunscreens (e.g. UVB-blocker octyl methoxycinnamate a.k.a. octinoxate) from degradation.

Summary:
Bisoctrizole (Tinosorb M) is a hybrid type sun blocking agent acting as both chemical and physical sunscreen. 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.

Details:
Bemotrizinol is both a chemical and physical UV blocking agent. It both absorbs, reflects and scatters ultraviolet rays in UVA and UVB range. It is marketed by Ciba Specialty Chemicals as Tinosorb M and is produced in the form of very small particles (nanoparticles), mostly ranging between 100 and 200 nm (similar to microfine zinc oxide and titanium dioxide). It is insoluble and is usually added to the water phase of a sunscreen as a 50% suspension (whereas zinc oxide and titanium dioxide are usually added to the oil phase). As of the time of this writing, bemotrizinolt is approved in Europe but not in the USA.

Bisoctrizole is highly stable and also has a stabilizing effect on other UV absorbers, particularly the UVB blocker octyl methoxycinnamate (octinoxate).

Unlike some other organic sunscreen agents, bisoctrizole has not been shown to have hormone-like (estrogenic) effects in cell cultures.

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.

Virtually no single sun blocking ingredient can provide complete, broad protection alone, including bisoctrizole. The good news is that bisoctrizole seems to be compatible with most other UVB and UVA blocking agents and even inhibits the degradation of some insufficiently photostable agents like octinoxate.