The cause of hiccups is still unknown, according to MSN Healthy Living. A hiccup is a quick contraction or spasm of the diaphragm, and while it can be irritating, it is rarely cause for concern.
Nerves in the chest give impulses to the muscles between the ribs and the diaphragm to contract spontaneously when a person hiccups. Emotional tension, excitement, overeating, consuming carbonated beverages, swallowing air, rapid temperature changes, smoking, and bingeing on alcoholic beverages are all examples of triggers that can cause a hiccup. Hiccups that last longer than two months may be a sign of sickness, but this is a rare occurrence.