Researchers at the Radboud University Nijmegen Medical Center in the Netherlands, collected blood samples from participants before and after they ate 48 g of chocolate, each day for four days.
The chocolate contained about 30 per cent cocoa.
They then exposed the blood cells to bacteria called Propionibacterium acnes, which contribute to acne when they grow inside clogged pores and cause pores to become inflamed, and to Staphylococcus aureus, another skin bacteria that can aggravate acne.
After eating chocolate, the seven participants' blood cells produced more interleukin-1b, a marker of immune system inflammation, when exposed to Propionibacterium acnes.
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In addition, eating chocolate increased production of another immune system factor called interleukin 10 after exposure to Staphylococcus aureus, MyHealthNewsDaily reported.
Interleukin 10 is thought to lower human bodies' defenses against microorganisms, and thus, higher levels of interleukin 10 could create conditions that allow bacteria to infect pimples, and worsen them, the researchers said.
Although there's a lot of talk about chocolate and other foods playing a role in acne, there's very little evidence to show they do, said Dr Kanade Shinkai, a dermatologist at the University of California, San Francisco School of Medicine, who specialises in acne treatments.
While there may be a subset of people whose acne is influenced by diet, this is probably not true for everyone, Shinkai was quoted as saying by the website.
Shinkai cautioned against broad dietary restrictions, such as avoiding diary, because diary products are important sources of calcium and vitamin D for many people, and the nutritional benefits of the products outweigh the impact of acne, she said.
The new study was published in the journal Cytokine.