There is no way to tell for sure, but I will say this...
I've had chemical peels to my lips in the past with no ill effects.
At the beginning of this, I was sure it was simply trauma related, but when the EC began to spread to surrounding tissues that were not traumatized, I felt there was no other explanation but infection.
The spread and deterioration was so rapid I strongly feel there is an infection present, and my dermatoligst precscribing and Antibiotic suggests to me he felt so as well.
Also, there were EC areas spreading in the inside of my lips reaching inside of my mouth where I can't apply the desonide because it's in my inner lips (and I would literally have to swallow it)... these areas seem to have cleared up during my course of the antibiotic.