Too much vitamin B12 may cause acne, or at least make it worse, according to a new study in the US.
"I think there's a link" between vitamin B12 and acne, Huiying Li, of UCLA, a co-author of the study, told Live Science.
The pharmacology professor found a molecular pathway that could explain the nexus, although that needs to be confirmed.
"There's still a lot to be studied in order to really understand if B12 causes acne," she said.
The study found that, in the presence of vitamin B12, the skin bacteria that are commonly linked to acne start pumping out inflammatory molecules known to promote pimples.
In the study, scientists investigated the differences between skin bacteria from people prone to acne and bacteria from people with clear-skinned faces. The researchers looked at the bacteria's gene expression, hoping to figure out why Propionibacterium acnes, which is the most common skin microbe, causes pimples in some people but not in others.
They found that vitamin B12 changed the gene expression of the skin bacteria, which is what could have led to the acne-promoting inflammation.