Why Would Botox Cause Lasting Acne Break Outs?

I have never had acne (I am 34) then I had Botox and 4 days later broke out and 5 months later it is still here. My Dr said it isn't the Botox but there are actually many discussion groups on the web w/ patients stating the exact same thing and when I call Allergan the rep said they are getting many calls about this but havent researched it yet. Many of the discussion groups people say the acne stays after Botox is gone. Without dismissing it as not possible, can a Dr explain what might be going on?