Tinosorb (Photostable UV Filters)

Tinosorb S and Tinosorb M target the same problem — UV-induced skin damage — through overlapping but distinct mechanisms, which is why they pair so well. Tinosorb S (bemotrizinol) is an oil-soluble organic molecule with two absorption peaks: around 310 nm in the UVB range and 340 nm deep into UVA-I. When it absorbs a UV photon, the molecule jumps to an excited state and then releases that energy as harmless heat rather than letting it reach skin cells or DNA. Its triazine backbone is unusually stable, so it returns to its ground state largely unchanged instead of fragmenting into reactive byproducts — the root of its photostability. That same stability lets it act as a photostabilizer for less robust actives such as avobenzone, intercepting energy from excited avobenzone molecules before they degrade. Tinosorb M (bisoctrizole) is structurally related but exists as sub-200 nm microfine organic particles suspended in the formula rather than dissolved in the oil phase. Because of that particle form, it protects through two pathways at once: molecular absorption like Tinosorb S, plus physical scattering and reflection of UV. This hybrid behavior bridges chemical and mineral filters, offering organic-filter aesthetics with some of the scattering you'd expect from a mineral. Together the two cover roughly 280 to 400 nm — genuine broad-spectrum range. In the EU, each is permitted up to 10% in finished products.

• Broad-spectrum UVA + UVB coverage spanning roughly 280-400 nm
• Strong photostability — Tinosorb S reportedly retains about 98% activity after 50 MEDs
• Helps stabilize avobenzone, slowing its photodegradation and UVA loss
• Tinosorb M's hybrid particle design scatters and absorbs UV at the same time
• Low systemic absorption at standard use levels in available pharmacokinetic data
• Low skin-sensitization profile across decades of global use

Two INCI names signal it: Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine (Tinosorb S) or Methylene Bis-Benzotriazolyl Tetramethylbutylphenol (Tinosorb M). The EU permits both up to 10% in finished products. Tinosorb M is supplied as a roughly 50% aqueous suspension, so the active-particle concentration in the final product is around half the listed suspension amount. In practice both filters tend to sit in the middle of an INCI list (very roughly 1-5% active) and are almost always paired with other filters for full-spectrum coverage. High-SPF European and Korean sunscreens that list either ingredient alongside ethylhexyl triazone or uvinul-a-plus tend to be among the most photostable systems on the market.

Pairs well with: Avobenzone (Butyl Methoxydibenzoylmethane), Ethylhexyl Triazone (Uvinul T 150), Uvinul A Plus (DHHB), Mexoryl SX (Ecamsule), Mexoryl XL (Drometrizole Trisiloxane), Zinc Oxide, Titanium Dioxide, Niacinamide (Vitamin B3), Antioxidants, Vitamin C (L-Ascorbic Acid), Vitamin E (Tocopherol)

1. https://pubmed.ncbi.nlm.nih.gov/11594052/
2. https://www.dermatologytimes.com/view/fda-proposes-expansion-of-us-sunscreen-ingredient-standards-with-bemotrizinol
3. https://en.wikipedia.org/wiki/Bemotrizinol
4. https://en.wikipedia.org/wiki/Bisoctrizole