Young men who ate up to 8 ounces of chocolate saw their average number of pimples skyrocket from fewer than four to as many as 70.
And the more chocolate they ate, the more they broke out -- a finding that further supports the idea that the worsening of acne was due to eating the chocolate, says study researcher Samantha Block, a second-year medical student at the University of Miami Miller School of Medicine.
Still, the study doesn't prove cause and effect.
Block and colleagues studied 10 men aged 18 to 35 who had previously been diagnosed with acne. Under the researchers' supervision, they ate as much pure chocolate as they wanted in one sitting, up to a maximum of three 4-ounce candy bars. Then they were told to follow their normal (chocolate-free) diet for a week.
At the start of the study, the men had an average of three pimples. By the fourth day, the figure had jumped to 13 and by the end of the week, they had an average of 18 pimples.
Also, participants who finished less than one 4-ounce chocolate bar had fewer than 10 pimples a week later, according to the study, presented here at the annual meeting of the American Academy of Dermatology.
But the young man who ate the most chocolate -- just about 8 ounces -- had 70 pimples by the seventh day. "The numbers speak for themselves," Block says.
The Role of Pure Chocolate
Previous studies looking at chocolate and acne used sweetened chocolate that contained sugar, milk, and other ingredients that themselves can aggravate the skin condition, says researcher Caroline Caperton, MD, MSPH, senior clinical research fellow in dermatology at the University of Miami.
The fact that the current study used unadulterated chocolate, made of 100% cocoa, is a major advantage, she says.
Some of the ingredients in pure chocolate that might exacerbate acne are caffeine and its cousin theobromine, which is known to have pore-clogging properties, Caperton tells WebMD.