So, when we fast we pretty much let the body and immune system clean things up, so my intuition would be that maybe your system is trying to do something with the acne? Maybe it has to get worse before it gets better? Bring things to a head?
For me, I get constipated when I fast and when I am constipated I always get acne. I eat a carnivore diet myself.
If you’re not feeling bloated/backed up, chances are this isn’t your issue though. I have a history of IBS-C.
I had a similar experience last week with the first 48 hour fast I’ve done in years. I wondered if it was related to the hormone changes that can occur during fasting, or some kind of systemic purge. I’m starting my next fast tonight, so I’m curious to see if it happens again.