Methylene Bis-Benzotriazolyl Tetramethylbutylphenol
Explained
This ingredient is also known as Tinosorb M or Bisoctrizole and is a bit of an overachiever in the sunscreen world.
It's a hybrid broad-spectrum filter that covers UVA and UVB (~280-400nm) with peak absorption around 305nm for UVB or 360nm for UVA (and a tiny bit in blue-light territory as well).
One of its best party tricks is photostability; it doesn't break down with repeated sun exposure and doesn't generate free radicals in the process either. You'll also see it paired with wobbly filters like avobenzone because it helps stabilize them.
The safety profile is assuring as well. Because it's a large molecule, it doesn't easily absorb into skin and rarely causes irritation.
It's approved in the EU, Asia, and Australia up to 10% and most formulas land somewhere in the 2-10% range.
You won't find it as a sunscreen active in the US, but it can make an appearance as a formula-protecting UV-absorber.
See all 1,088 products with Methylene Bis-Benzotriazolyl Tetramethylbutylphenol
