Avobenzone

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Avobenzone

Chemical formula	C₂₀H₂₂O₃
Molar mass	310.387 g mol⁻¹
Systematic name	1-(4-methoxyphenyl)-3-(4-tert- butylphenyl)propane-1,3-dione
Complete data

Avobenzone (trade names Parsol® 1789, Eusolex® 9020, Escalol® 517 and others, INCI Butyl Methoxydibenzoylmethane) is an oil soluble ingredient used in sunscreen products to absorb both UVA and UVB rays. Its ability to absorb ultraviolet light over a wider range of wavelengths than many organic sunscreen agents has led to its use in many commercial preparations marketed as "broad spectrum" sunscreens. According to doctors, "the most effective sunscreens contain avobenzone and titanium dioxide." ^[1]

Avobenzone has been shown to degrade significantly in light, [1] [2] [3] resulting in less protection over time. This degradation can be reduced by using a photostabilizer, like octocrylene. Other photostabilizers include:

4-methylbenzylidene camphor (USAN Enzacamene)
Tinosorb® S (USAN Bemotrizinol, INCI Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine)
Tinosorb® M (USAN Bisoctrizole, INCI Methylene Bis-Benzotriazolyl Tetramethylbutylphenol)
Butyloctyl Salicylate
Hexadecyl Benzoate
Butyloctyl Benzoate
Mexoryl® SX (USAN Ecamsule, INCI Terephthalylidene Dicamphor Sulfonic Acid)
Diethylhexyl 2,6-Naphthalate
Parsol® SLX (INCI Polysilicone-15)

Avobenzone shows to degrade faster in light in combination with mineral UV absorbers like zinc oxide and titanium dioxide. The FDA prohibits this combination. With the right coating of the mineral particles this reaction can be reduced. Avobenzone reacts with minerals to form colored complexes. Manufacturers of avobenzone, like DSM recommend to include a chelator to prevent this from happening. They also recommend to avoid the inclusion of iron and ferric salts, heavy metals, formaldehyde donors and PABA and PABA esters.

The makers of Coppertone advise that avobenzone binds iron and can cause staining of clothes washed in iron-rich water.