Sneezes triggered by eating chocolate are due to a trigeminal nerve reaction to a stimulant, states The Atlantic. This reaction is similar to the “photic sneeze reflex” that causes some people to sneeze in bright sunlight.
The reason for the reaction is not clearly understood, and there is no known cure. It is thought that some intertwining of the nerves that connect the eyes nose and mouth sends a mixed message to the brain and results in a sneeze. The term given to this chocolate-sneezing phenomenon is also “photic sneeze reflex." Somewhere between 18 and 35 percent of the population is affected by this hereditary condition.