Chocolate has not been found to cause acne, according to HowStuffWorks. Also, other foods commonly blamed to cause acne, such as pizza or chips, do not cause it.
According to WebMD, the real cause of acne is when there is too much sebum produced by the oil glands. Sebum is a waxy substance that combines with dead skin cells and then clogs the skin pores. The acne develops when bacteria increases and inflames the clogged pores, causing them to be red and swollen.
Dr. Albert Kligman with the University of Pennsylvania conducted an experiment to see whether or not acne was caused by chocolate. The experiment consisted of two groups of acne-predisposed teens. Some were given real chocolate bars, while the others were given chocolate-free bars that tasted like chocolate. He concluded that there was not a variation in either group.