Butyl Methoxydibenzoylmethane

Butyl methoxydibenzoylmethane (avobenzone) is a UVA filter typically used around 2–3% in sunscreens and is generally well-tolerated, but it has documented potential to sting or irritate, especially on compromised skin or near the eyes. Patch-test data suggest irritant reactions are uncommon but do occur, and true allergy is rare yet possible. Given real-world cumulative exposure (daily application, reapplication, and combinations with other UV filters/solvents), I rate it as mild irritancy risk for sensitive and eczematous patients. Safety Notes: Butyl Methoxydibenzoylmethane (avobenzone) is an oil-soluble UVA filter used almost exclusively in leave-on sun care and daily moisturizers with SPF; at the low end, it appears around ~0.1–1% in lower-SPF or combination-filter formulas where it is supported by other UVA/UVB filters. High-strength OTC sunscreens in the US commonly use avobenzone at 2–3%, and the highest consumer-available products reach 5% (the FDA monograph maximum for avobenzone in OTC drug sunscreens), typically requiring photostabilizers (e.g., octocrylene) and appropriate solvent/emollient systems.