Avobenzone (trade names Parsol 1789, Milestab 1789, Eusolex 9020, Escalol 517, Neo Heliopan 357 and others, INCI Butyl Methoxydibenzoylmethane) is an organic molecule and an oil-soluble ingredient used in sunscreen products to absorb the full spectrum of UVA rays.

As of 2021, the FDA announced that they do not support avobenzone as being generally recognized as safe and effective (GRASE)[1] citing the need for additional safety data.

[2] Pure avobenzone is a whitish to yellowish crystalline powder with a weak odor,[3] dissolving in isopropanol, dimethyl sulfoxide, decyl oleate, capric acid/caprylic, triglycerides and other oils.

[6] Avobenzone, a petroleum-based sunscreen active ingredient,[7] is not generally recognised as safe and effective (GRASE) by the FDA for lack of sufficient data to support this claim.

Also, when it is irradiated with UVA light, it generates a triplet excited state in the keto form which can either cause the avobenzone to degrade or it can transfer energy to biological targets and cause deleterious effects.

Data presented to the Food and Drug Administration by the Cosmetic, Toiletry and Fragrance Association indicates a −36% change in avobenzone's UV absorbance following one hour of exposure to sunlight.

[24] Formulations of avobenzone with hydroxypropyl-beta-cyclodextrin have shown significant reduction in photo-induced degradation, as well as decreased transdermal penetration of the UV absorber when used in high concentrations.

[citation needed] Avobenzone in sunscreen may stain clothes yellow-orange and make them sticky if washed in iron-rich water, as it reacts with iron to produce rust.

[citation needed] Avobenzone also reacts with boron trifluoride to form a stable crystalline complex that is highly fluorescent under UV irradiation.