Vitamin B12 Injections: What You Need To Know What Happens When You're Allergic to Vitamin B12 8 things that could be triggering your acne , 1) Hormonal imbalance , 2) Highly processed diet, 3) Dairy, 4) B12 injections, 5) Bacteria, 6) Stress, 7) Dirty makeup brushes, 8) Over exfoliation, If Vitamin B12 Deficiency Vitamin B12 deficiency happens when the body does not have enough vitamin B12. Vitamin B12 is important for making healthy red blood cells and keeping nerves