Most people who are allergic to chocolate aren't having a reaction to cocoa or any of chocolate's other official ingredients. No, the flare ups are most likely triggered by the ground-up cockroach parts that contaminate every batch.
According to ABC News, the average chocolate bar contains eight insect parts. Anything less than 60 insect pieces per 100 grams of chocolate (two chocolate bars' worth) is deemed safe for consumption by the Food and Drug Administration.
Allergists say most foods contain natural contaminants. Aside from chocolate, cockroach parts also make their way into peanut butter, macaroni, fruit, cheese, popcorn and wheat. The roach bits can affect people with asthma, as well causing migraines, cramps, itching or hives in people who are allergic to them.
The first cockroach allergy was reported in 1943, and skin testing for cockroaches began in 1959. Cockroach allergies can be treated with allergy shots that contain trace amounts of the insect. [Could Edible Bugs Solve World Hunger?]
According to Morton Teich, an allergist at Mount Sinai School of Medicine, contamination by cockroaches and their droppings is unavoidable, because it happens at cocoa beans' source — the farms where they are produced. Preventing them from infiltrating the harvest would require the use of more pesticides, which Teich says are much worse for you than consuming a few extra bug parts.
Avoiding insects in your food is "almost impossible," Teich told ABC. "You probably would have to stop eating completely."