Chemical UVA sunscreen/sunblock agent: Avobenzone (Parsol 1789, Eusolex 9020, Escalol 517)

Generic name: Avobenzone; butyl methoxydibenzoylmethane

Brand(s): Parsol 1789, Eusolex 9020, Escalol 517 and others

Type: Chemical

Range of UV spectrum covered: UVA (both UVA-1 and UVA-2)

Wavelengths covered: 310-400 nm, which covers all of UVA

Stability:
Avobenzone degrades in the sunlight, which leads to loss of protective effect. The rate of degradation can be reduced by photostabilizers. However, photostabilizers may increase the risk of skin irritation.

Summary:
Abobenzone is one of the very few chemical sunscreens with good coverage of UVA spectrum. Abobenzone is relatively nonirritating, although, as with many skin care ingredients, the possibility of low-level topical or systemic toxicity with long-term use remains unresearched. Abobenzone degrades in sunlight (especially if mixed with inorganic sunscreens) and loses effectiveness over time. Development of stabilized and microencapsulated versions of avobenzone is promising and may reduce the above drawbacks.

Details:
Avobenzone is an oil soluble chemical agent capable of absorbing light throughout the entire UVA spectrum. It is one of the very few comprehensive chemical UVA sun blocks in widespread use.

Avobenzone appears to be relatively non-toxic and rarely causes skin irritation. However, as with many synthetic chemicals, it is unclear whether avobenzone or its degradation products may produce low-level toxicity with long-term use. Considering that some of the topically applied avobenzone is absorbed into systemic circulation, it is not recommended for use in children or during pregnancy.

In the sunlight, avobenzone degrades at considerable rate, resulting in less protection over time. After a day in sunlight, most of the applied avobenzone will have degraded. Photostabilizers, such as octocrylene, reduce the rate of avobenzone of degradation. However, they may add to the risks of irritation and/or low-level toxicity. On the other hand, inorganic sunscreens, such as zinc oxide and titanium dioxide tend to increase degradation of avobezone in the sunlight. Therefore, combining avobenzone with inorganic sunscreens remains controversial. It is approved in Europe but not in the USA. The risk of combining avobenzone with inorganic sunscreens may be reduced by using encapsulated versions of the former (see below) and/or coated versions of the latter.

A number of companies have developed proprietary technologies stabilizing for abobenzone, including Helioplex(TM), Active Photo Barrier Complex (TM), Dermaplex (TM), SunSure (TM) and AvoTriplex (TM). While they all seem to reduce abobenzone degradation to some degree, full benefits and risks of their long-term use remain to be determined. Also, skin care companies are developing microencapsulated versions of avobenzone, which will be more stable and safer to mix with other agents, including inorganic sunscreens. Notably, microencapsulated avobenzone and its degradation products, will not be absorbed (or will be much less absorbed) into the skin or systemically, improving the safety profile. If all of these promises are fulfilled and verified, avobenzone will approach the ideal for the chemical UVA block. That is not a sure bet, however.