What it is
Bisoctrizole is a benzotriazole-based UV filter often called a hybrid because it combines features of organic and mineral filters. It is poorly soluble in both oil and water, so it is supplied as an aqueous dispersion of microfine particles, typically stabilized with a surfactant such as decyl glucoside. These particles both absorb ultraviolet light and reflect and scatter it, giving broad coverage across the UVB and UVA range with absorption peaks reported near 305 and 360 nm. It is highly photostable and can help stabilize less stable filters such as octinoxate (octyl methoxycinnamate).
Spectrum coverage
UVA1 · UVA2 · UVB
Regional approval · max %
Safety & warnings
Because of its large particle size, bisoctrizole is reported not to penetrate into the skin, and references note that, unlike some older organic filters, it does not show estrogenic activity. Like mineral filters, its particulate nature can leave a slight white cast, which may be more visible on deeper skin tones. It is generally regarded as well tolerated, though anyone with reactive skin can patch test a new sunscreen.
Origin & sourcing
It is a synthetic organic compound produced by chemical manufacturers and supplied as a particulate dispersion for use in sunscreens. It is not derived from a natural source.
History
The filter was developed and marketed by Ciba (later part of BASF) under the trade name Tinosorb M and was approved for use in the European Union around 2000. It is also sold under other trade names including Parsol Max, Eversorb M, and Milestab 360, and remains approved in the EU and many other regions while still under review in the United States.
Questions everyone asks
Is bisoctrizole a mineral or chemical sunscreen?
It is an organic (carbon-based) filter, but it is formulated as microfine particles and works partly by scattering light, so it is often described as a hybrid between chemical and mineral filters.
Why isn't it in US sunscreens?
Bisoctrizole is approved in the EU, Korea, Japan, and many other markets, but it has not yet completed US FDA review, so it is not currently available in US over-the-counter sunscreens.
Does it protect against UVA?
Yes. It provides broad-spectrum coverage across both UVB and UVA wavelengths and is highly photostable, which is why it is often paired with other filters.