[1] Once triggered, the reflex causes a strong contraction of the diaphragm followed about a quarter of a second later by closure of the epiglottis[citation needed], a structure inside of the throat, which results in the "hic" sound.

[5] A hiccup consists of a single or a series of breathing diaphragm spasms, of variable spacing and duration, and a brief (less than one half second), unexpected, shoulder, abdomen, throat, or full body tremor.

[citation needed] An international respiratory research group composed of members from Canada, France, and Japan proposed that the hiccup is an evolutionary remnant of earlier amphibian respiration.

[20] Amphibians such as tadpoles gulp air and water across their gills via a rather simple motor reflex akin to mammalian hiccuping.

Additionally, this group (C. Straus et al.) points out that hiccups and amphibian gulping are inhibited by elevated CO2 and may be stopped by GABAB receptor agonists, illustrating a possible shared physiology and evolutionary heritage.

These proposals may explain why premature infants spend 2.5% of their time hiccuping, possibly gulping like amphibians, as their lungs are not yet fully formed.

[26] There are many folk remedies for hiccups, including headstanding, drinking a glass of water upside-down, being frightened by someone, breathing into a bag, eating a large spoonful of peanut butter and placing sugar on or under the tongue.

The index or middle fingers are inserted into the indents and pressed firmly for sixty seconds as long, deep breaths are taken.

[29] A simple treatment involves increasing the partial pressure of CO2 and inhibiting diaphragm activity by holding one's breath or rebreathing into a paper bag.

[30] Other potential remedies suggested by NHS Choices include pulling the knees up to the chest and leaning forward, sipping ice-cold water and swallowing some granulated sugar.

[33] In 2021 a scientific tool with a similar basis was tested on 249 hiccups subjects; the results were published in the Journal of the American Medical Association (JAMA).

This study supports the use of FISST as an option to stop transient hiccups, with more than 90% of participants reporting better results than home remedies.

HiccAway stops hiccups by forceful suction that is being generated by diaphragm contraction (phrenic nerve activity), followed by swallowing the water, which requires epiglottis closure.

[36] In Baltic, German, Hungarian, Indian, Romanian, Slavic, Turkish, Greek and Albanian tradition, as well as among some tribes in Kenya, for example in the folklore of the Luo people, it is said that hiccups occur when the person experiencing them is being talked about by someone not present.