How vitamin B12 makes pimples pop up

Vitamin B12 causes a normal skin bacteria to produce pimple-promoting chemicals. 

Both people with clear skin and those with acne have Propionibacterium acnes living on their skin. But bacteria from acne sufferers have a different metabolism than microbes from the pimple-free, researchers report June 24 in Science Translational Medicine. Microbes from the acne-ridden have 109 genes that are more active than normal and 27 that are less active. Taking vitamin B12 can cause similar changes in these bacteria, the researchers found.

Vitamin B12, which is important for making red blood cells and for brain function, has long been known to cause acne in some people, but researchers didn’t understand why. Dezhi Kang of the UCLA David Geffen School of Medicine and colleagues gave vitamin B12 supplements to 10 people with clear skin. One developed acne a week later.

Bacteria from all of the vitamin-takers stopped producing as much vitamin B12 because the microbes were getting the vitamin from their hosts, the researchers learned. In the person who got acne, that drop in vitamin B12 production also shifted the bacteria’s metabolism, causing them to make chemical precursors of porphyrins. Porphyrins cause inflammation in the skin, leading to pimples.

The research could lead to new acne treatments that alter the metabolism of friendly bacteria in healthy ways.