Too Much of a Good Thing: How Vitamin B12 Triggers Acne Breakouts I got B12 injections in September and my skin started getting bad in October. I stopped the B12 in February when I finally realised that was causing the acne. My skin is soooo much better now, I would Do vitamin B12 intramuscular injections cause acne? Is B12 making you break out? It's possible. We've found in our own experience and in clinical studies that certain forms of vitamin B12 can trigger inflammatory acne for some individuals.