Chemical UVA+UVB sunscreen/sunblock: Bemotrizinol (Tinosorb S)

Generic name: Bemotrizinol; bis-ethylhexyloxyphenol methoxyphenyl triazine

Brand(s): Tinosorb S

Type: Chemical

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 348 nm

Stability:
Bemotrizinol is stable when exposed to sunlight. It can also partly protect other chemical sunscreens (e.g. UVA-blocker avobenzone) from degradation.

Summary:
Bemotrizinol is one of the very few chemical sunscreens with good coverage of the entire UVA spectrum. It also provides some UVB protection. Furthermore, it does not degrade under sunlight and is not significantly absorbed into the skin. 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 an oil soluble chemical agent absorbing ultraviolet rays in both UVA and UVB range. It is patented and marketed by Ciba Specialty Chemicals as Tinosorb S. It has an important advantage of being photostable, i.e. it does not degrade and lose effectiveness on exposure to sunlight. Furthermore, its presense can at least partially protect less photostable UV blockers (e.g. UVA-blocker avobenzone) from degradation. As of the time of this writing, it is approved in Europe and Australia but not in the USA. Unlike some other organic sunscreen agents, bemotrizinol has not been shown to have hormone-like (estrogenic) effects in cell cultures.

Bemotrizinol appears to be relatively non-toxic and rarely causes skin irritation. However, as with many synthetic chemicals, it is unclear whether bemotrizinol may produce low-level skin damage and/or systemic effects with long-term use. More research on bemotrizinol safety is needed.

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