A sneeze (or sternutation) is a semi-autonomous, convulsive expulsion of air from the lungs, most commonly caused by foreign particles irritating the nasal mucosa. Sneezing can further be triggered through sudden exposure to bright light, a particularly full stomach, or as a result of unexpected, climatic variations in one's environment such as rapid changes in temperature and humidity levels. This could cause one or multiple sneezes.
Some people like myself will sneeze 5 or 6 times in a row. I have allergies, so when something bothers me like a scent, or dust, I will sneeze over and over again. Sneezing is actually the bodies way of getting rid of the "yuck" or the foreign matter that enters our lungs and nostrils.