What causes hiccups in humans?

Hiccups occur when a person’s air intake is instantly blocked. It can happen for no apparent reason. Hiccups are usually a minor nuisance, but prolonged hiccups can indicate a serious medical problem. When hiccups develop, it is due to the sudden involuntary contraction of the diaphragm simultaneously with the contraction of the vocal cords or larynx and the complete closure of the glottis. This results in a sudden rush of air into the lungs and the familiar hiccup sound. Most people get hiccups from time to time, and they usually go away without treatment within a few minutes.