Avobenzone (INCI: Butyl methoxydibenzoylmethane) is one of the most common chemical sunscreen filters that targets UVA rays.
Chemically, it comes in a yellowish powder form and practically does not have odor. It is oil soluble and can be solubiliced some tryglycerides forms too.
Avobenzone spectrum range and stability
Avobenzone covers both UVA1 and UVA2 rays (310-400 nm wavelenghts) with a peak at 357 nm, making it one of the best UVA filters available worldwide. It does not cover UVB rays.
Even though avobenzone offers a high UVA protection, it is highly not photostable, this is that it degrades very fast when it is exposed to the sun. The good news are that it can be stabilized when it is combined with other sunscreens filters such as octocrylene, Tinosorb M, Tinosorb S…
Avobenzone free radical damage
Avobenzone does not produce free radicals on its own, but when avobenzone and octinoxate are combined in the same sunscreen they become more unstable and they produce free radical damage that it can persist even after the product exposure has stopped.1Sayre RM, Dowdy JC, Gerwig AJ, Shields WJ, Lloyd RV. Unexpected photolysis of the sunscreen octinoxate in the presence of the sunscreen avobenzone. Photochem Photobiol. 2005;81(2):452-456. doi:10.1562/2004-02-12-ra-083.1
So it is always advised to avoid sunscreens that contains both sunscreen filters.
Avobenzone absorption and allergies
Avobenzone has a good safety profile, even though avobenzone can be absorbed through the skin and reach inside the body in higher levels than other sunscreen filters it doesn’t mean it poses any risk, and at least today it has not shown to cause any endocrine or cancer related problems.
As for allergies, avobenzone does not cause skin irritation and just a few cases of contact dermatitis have been reported.2Berne B, Ros AM. 7 years experience of photopatch testing with sunscreen allergens in Sweden. Contact Dermatitis. 1998;38(2):61-64. doi:10.1111/j.1600-0536.1998.tb05653.x
Environment influence of avobenzone
Unlike other sunscreen filters, avobenzone is coral reef safe since it has not been shown to be damaging to coral reefs or other marine or aquatic, furthermore there is no evidence that it will bioaccumulate in the environment.