I have seen on some sort of facewash that it uses “active oxygen.” Of course, they neglect to mention what exactly that is or how it works. I’m assuming it doesn’t mean much and the true active ingredient is something else, but I’m curious. Does anybody know?
I thought about it for three seconds, and concluded “SCAM!”
But then I did a Google search, and found an approximately equal mix of:
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Biology and chemistry articles that were way over my head.
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Webpages hawking various prepartions, pills, tinctures and potions.
My WAG: It is probably Yet Another phrase that has real scientific meaning that is being missapplied to sell acne cream. But that’s just a WAG. Surely someone will come along who knows what they’re talking about. 
(Hopefully they’ll say it works, so I can rush out and buy some. I’m having this hideous break-out on my chin . . .)
Active oxygen is a term applied to the oxygen containing radicals produced by the breakdown of compounds such as benzoyl peroxide. Benzoyl peroxide has limited solubility in water, so the rate at which peroxide particles in pimple cream produce cleansing radicals depends largely on how finely the material is ground. That fact leads to all sorts of wild advertising claims as to who’s acne cream produces the most “active oxygen.”
If you want to frighten yourself over the connection between pimple cream and cancer, take a look at this search.
As the gal from Mars posted, the term “active oxygen” has real scientific meaning, but its also misused as an advertising ploy.
Please don’t take the cancer stuff too seriously. Radicals can be unhealthy, but benzoyl peroxide has been a safe effective ingredient in pimple cures for ages.