Hiccups are a complicated phenomenon. No one can really explain why people hiccup, but certain triggers have been identified and the physiology is understood. When you hiccup, your diaphragm -- which is the muscle between your chest and abdomen - contracts, and it causes you to inhale too quickly. Then your glottis closes and the space around your vocal cords snaps shut; you end up making a strange sound. The possible triggers of hiccups include eating too much, imbibing excessive amounts of alcohol, smoking cigarettes and stress. In addition, certain diseases and drugs have been known to bring about hiccups -- chemotherapy included.
Hiccups normally go away within minutes or hours. There are all types of home remedies for these cases of hiccups, like holding your breath, swallowing sugar or drinking ice water. However, some cases of persistent or intractable hiccups stay for days or months. These types can sometimes be cured by medications like chlorpromazine and metoclopramide.