Methylene Bis-Benzotriazolyl Tetramethylbutylphenol

Methylene Bis-Benzotriazolyl Tetramethylbutylphenol (Tinosorb M) is a photostable, insoluble particulate UV filter typically used around 1–10% in sunscreens and is generally well-tolerated in clinical use, including sensitive-skin populations. Reported irritation and sensitization rates are low, with reactions more often attributable to the overall sunscreen vehicle rather than this filter itself; however, as a particulate dispersed in formulations, it can still provoke mild stinging or irritation in highly reactive or barrier-impaired skin. Given its broad use and low intrinsic reactivity but non-zero risk in compromised skin, it fits best as very gentle rather than inert. Safety Notes: In commercial sunscreens and daily moisturizers with SPF, Methylene Bis-Benzotriazolyl Tetramethylbutylphenol (also known as Tinosorb M) is observed at low levels (~0.1–1%) mainly as a supportive UV filter/photostabilizer in multi-filter systems. High-protection OTC sunscreens marketed in regions where it is permitted (notably EU/UK and many other non-US markets) commonly use ~2–8%, with the highest consumer-available formulas reaching the EU maximum of 10% for leave-on products; it is rarely used in rinse-off products due to particulate dispersion and film-forming requirements.