Avobenzone

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 the full spectrum of UVA rays. It is a dibenzoylmethane derivative. 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.

Avobenzone was patented in 1973 and was approved in the EU in 1978. It was approved by the FDA in 1988. Its use is approved world wide.

Avobenzone has been shown to degrade significantly in light, resulting in less protection over time. The UV-A light in a day of sunlight in a temperate climate is sufficient to break down most of the compound. 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)
 * Corapan® TQ (INCI Diethylhexyl 2,6-Naphthalate)
 * Parsol® SLX (INCI Polysilicone-15)
 * Oxynex® ST (INCI Diethylhexyl Syringylidene Malonate)

Complexing avobenzone with cyclodextrins may also increase its photostability.

According to some studies, "the most effective sunscreens contain avobenzone and titanium dioxide." The combination with TiO2 is approved for use in the EU, but in the US the FDA has yet to approve this, stating (in 1997) that "until complete and adequate data have been submitted, the agency has no basis to allow other avobenzone combinations" (containing titanium dioxide).(this is wrong)  Avobenzone can degrade faster in light in combination with mineral UV absorbers like zinc oxide and titanium dioxide, though with the right coating of the mineral particles this reaction can be reduced. A manganese doped titanium dioxide may be better than undoped titanium dioxide to improve avobenzone's stability.

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.