Ecamsule (Mexoryl SX)

Where it’s restricted

Named in the law or guidance

Also not allowed under mineral-only rules

Ecamsule (Mexoryl SX) isn’t named in these laws, but they allow only mineral (zinc oxide or titanium dioxide) sunscreens, so a product containing it is excluded anyway.

• Maui County (Maui, Molokaʻi, Lānaʻi) (in force since October 1, 2022)
• Hawaiʻi County (Big Island) (in force since December 1, 2022)

Why it’s regulated

In 2015 the FDA proposed that ecamsule at up to 10 percent is not generally recognized as safe and effective (GRASE) and is misbranded in over-the-counter sunscreens, because the available data were insufficient. The FDA said the data submitted were not enough to assess ecamsule's dermal safety, including its potential to cause irritation and sensitization.

What the reef research says

A 2019 study by Fel et al. tested ecamsule on Stylophora pistillata coral in the laboratory. The coral's symbiotic algae were the measured organism, and the photosynthetic efficiency of those algae was the endpoint. In the tests, ecamsule showed no toxicity at nominal concentrations up to 5000 µg/L. Its measured water concentrations matched the nominal doses because it dissolves in water. A 2021 critical review of organic UV filters and corals cites this study for the 5000 µg/L figure and notes that a single endpoint makes it premature to rank the filters against each other. The review also says that overall conclusions on UV filter toxicity to corals are limited by the small amount of data.

• Fel et al. (2019), Photochemical response of the scleractinian coral Stylophora pistillata to some sunscreen ingredients (Coral Reefs)
• A Critical Review of Organic Ultraviolet Filter Exposure, Hazard, and Risk to Corals (PMC8048829)
• FDA proposed order: Over-the-Counter Sunscreen Drug Products, Regulatory Status of Ecamsule (Federal Register, 25 Feb 2015)

Related ingredients: Avobenzone, Drometrizole Trisiloxane (Mexoryl XL), Ethylhexyl Triazone (Uvinul T 150)

Last reviewed October 14, 2026.