A hiccup is a reflex: the diaphragm and nearby breathing muscles contract suddenly, then the opening between the vocal cords closes quickly. That closure makes the familiar “hic” sound. Common short-lived triggers include a stretched stomach, swallowing air or sudden changes in eating and drinking, but many ordinary bouts have no obvious single cause.
A brief breathing reflex
The diaphragm is a broad muscle beneath the lungs that helps draw air in. During a hiccup, it contracts involuntarily. The glottis—the opening between the vocal cords—then closes abruptly, briefly interrupting the incoming air and making the characteristic sound. A hiccup is therefore a coordinated reflex involving breathing muscles and the throat, not a deliberate breath. [1]
Why a hiccup starts
Short bouts can follow stomach distension, eating quickly, swallowing air, carbonated drinks or a sudden change in temperature. These are common associations, not a guaranteed cause in every episode. Nerves that carry signals from the chest and abdomen connect with the reflex pathway, so different kinds of irritation can set it off. Often no specific trigger is identified. [2]
Why most episodes stop on their own
In most people, hiccups last only a short time and resolve without a clear intervention. Scientists describe the muscle and throat actions well, but the evolutionary purpose of the reflex in adults remains uncertain. Hiccups before birth and in infancy have prompted hypotheses about breathing-muscle development, but they do not establish a definite function for adult hiccups.
When hiccups need medical attention
Hiccups that continue for a long time are uncommon and can interfere with eating, sleeping or breathing. Persistent symptoms may have an underlying medical cause, so a health professional should assess them. This explainer covers the basic reflex and is not a diagnosis.
Sources and evidence
- MedlinePlus — Hiccups ↗
U.S. National Library of Medicine overview of the diaphragm movement and common triggers.
- Hiccups: A Non-Systematic Review — PubMed ↗
Clinical review of hiccup physiology, common causes and persistent episodes.
Sources consulted: 14 October 2026. Written with AI assistance and checked against the linked references; not independently reviewed by a subject specialist. Sources do not endorse this article. See our editorial policy.
Revision: Initial publication; the explanation was checked against a National Library of Medicine reference and clinical review.