Hiccups are sudden, involuntary contractions of the diaphragm followed by rapid closure of the vocal cords that produce the characteristic “hic” sound. Nearly everyone experiences hiccups at some point in life. Most episodes last only a few minutes and resolve on their own, but in rare cases hiccups persist for days or longer and may indicate an underlying medical condition. Although usually harmless and even humorous, hiccups provide an interesting example of how the nervous system controls breathing and reflexes.
Scientists classify hiccups as a reflex involving the diaphragm, intercostal muscles, vagus nerve, phrenic nerve, and brainstem. The reflex likely evolved for reasons that remain unclear, although some researchers propose links to primitive breathing mechanisms or developmental processes in infants. Understanding how hiccups work helps explain both their common triggers and the methods used to stop them.
Key Takeaways: Hiccups
- Hiccups are involuntary contractions of the diaphragm followed by closure of the vocal cords.
- The sound occurs when air rushes into the lungs and the glottis suddenly closes.
- Most hiccups last only a few minutes and resolve without treatment.
- Common triggers include eating too quickly, swallowing air, carbonated beverages, and sudden temperature changes.
- Persistent hiccups lasting more than 48 hours may signal an underlying medical condition.
- Treatments range from simple breathing techniques to medications or medical procedures in severe cases.
- Hiccups are common in babies and occur in many animal species.
What Are Hiccups?
A hiccup is a reflex involving the respiratory system. It begins with a sudden contraction of the diaphragm, the dome-shaped muscle that separates the chest cavity from the abdomen and plays a central role in breathing.
Immediately after the diaphragm contracts, the vocal cords (glottis) close abruptly. This closure interrupts the incoming airflow and produces the distinctive “hic” sound.
The scientific term for hiccups is singultus, derived from the Latin word singult, meaning “to catch one’s breath while sobbing.”
In medical terminology, hiccups are considered a reflex arc that includes:
- Sensory pathways (vagus nerve, phrenic nerve, and sympathetic nerves)
- Central processing in the brainstem
- Motor pathways to the diaphragm and respiratory muscles
Because hiccups involve both nerves and muscles, disturbances anywhere along this reflex pathway can trigger them.
Global Terminology and Cultural Names for Hiccups
Different languages use distinctive words that imitate the hiccup sound.
Examples include:
- English: hiccup or hiccough
- French: hoquet
- Spanish: hipo
- German: Schluckauf
- Japanese: shakkuri
- Italian: singhiozzo
Many languages use onomatopoeic terms that mimic the sound of the reflex.
How Hiccups Work
Hiccups occur through a reflex mechanism that involves the diaphragm, breathing muscles, nerves, and the brainstem.
The process typically follows these steps:
- Trigger or stimulation occurs
Irritation of the diaphragm or associated nerves initiates the reflex. - Diaphragm contracts suddenly
The diaphragm pulls downward quickly, similar to the start of inhalation. - Air rushes into the lungs
The sudden contraction draws air inward. - Glottis closes abruptly
The vocal cords snap shut just after the air enters. - The “hic” sound occurs
The closure interrupts airflow, producing the characteristic sound.
This reflex repeast rhythmically, producing a series of hiccups.
The Hiccup Reflex Arc
Researchers describe a hiccup reflex arc involving three major components:
1. Afferent (sensory) pathways
These nerves detect irritation or stimulation and send signals to the brain:
- Vagus nerve
- Phrenic nerve
- Sympathetic nerves in the chest
2. Central processing
Signals are processed in areas of the brainstem that regulate breathing, likely involving the medulla and nearby structures.
3. Efferent (motor) pathways
Motor signals return to the muscles responsible for the hiccup:
- Diaphragm
- Intercostal muscles
- Vocal cords
Because multiple nerves and muscles participate in the reflex, a wide variety of stimuli can trigger hiccups.
Types of Hiccups
Physicians classify hiccups based on how long they last.
| Classification | Duration | Description |
|---|---|---|
| Acute hiccups | Seconds to hours | Most common form; usually harmless |
| Persistent hiccups | More than 48 hours | May indicate irritation of nerves or organs |
| Intractable hiccups | More than 1 month | Rare and often associated with serious disease |
Transient Hiccups
Transient hiccups are the most common type. They last from a few seconds to several minutes and resolve without treatment. Most people experience this type after eating or drinking.
Persistent Hiccups
Persistent hiccups last longer than 48 hours. They result from irritation of the diaphragm, nerve disorders, gastrointestinal problems, or certain medications.
Persistent hiccups may interfere with sleep, eating, or speaking.
Intractable Hiccups
Intractable hiccups last longer than one month. These are rare but can indicate serious underlying medical conditions involving the nervous system, chest, or abdomen.
Intractable hiccups sometimes require medical evaluation and treatment.
Causes of Hiccups
Hiccups occur when something irritates the diaphragm or the nerves that control it. Many everyday activities can trigger this reflex.
Common Causes
Most transient hiccups occur due to minor irritation or stimulation of the diaphragm.
Common triggers include:
- Eating too quickly
- Overeating
- Swallowing air while eating or drinking
- Carbonated beverages
- Alcohol consumption (irritates the stomach lining, relaxed the esophageal sphincter, and expands the stomach)
- Sudden stomach expansion
- Temperature changes in food or drinks
- Emotional excitement or stress
- Sudden temperature changes in the environment
Medical Causes
Persistent or intractable hiccups may arise from underlying medical conditions affecting the nervous system, chest, or abdomen.
Possible medical causes include:
- Gastroesophageal reflux disease (GERD)
- Stomach or intestinal irritation
- Liver disease
- Pneumonia
- Tumors affecting the chest or brain
- Stroke
- Brain injury
- Multiple sclerosis
Medication-Related Causes
Some medications can trigger hiccups as a side effect, including:
- Corticosteroids
- Benzodiazepines
- Chemotherapy drugs
- Anesthesia medications
In many cases, removing the trigger stops the hiccups.
Diagnosing the Cause of Persistent Hiccups
When hiccups last for an extended period, physicians perform diagnostic tests to identify the underlying cause.
Evaluation may include:
Medical history and physical examination
Doctors look for symptoms suggesting gastrointestinal, neurological, or respiratory disorders.
Laboratory tests
Blood tests may identify infections, metabolic imbalances, or kidney problems.
Imaging tests
Possible imaging methods include:
- Chest X-ray
- CT scan
- MRI scan
These tests help detect tumors, inflammation, or structural abnormalities affecting the diaphragm or nerves.
Treatments for Hiccups
Most hiccups resolve without treatment, but many methods stop them more quickly. Treatments generally aim to interrupt the hiccup reflex arc.
Treatments for Transient Hiccups
Common home remedies attempt to reset breathing patterns, stimulate the vagus nerve, or increase carbon dioxide levels in the blood.
Examples include:
- Holding the breath
- Breathing slowly into a paper bag – Breathing into a paper bag should not be used if someone has heart or lung disease, because it reduces oxygen levels.
- Drinking cold water quickly
- Gargling with water
- Swallowing a teaspoon of sugar or honey
- Pulling gently on the tongue
- Stimulating the gag reflex
Many of these methods increase carbon dioxide in the bloodstream or stimulate nerves connected to the hiccup reflex.
Although widely used, not all remedies work consistently because hiccups often stop spontaneously.
Treatments for Persistent or Intractable Hiccups
If hiccups last longer than 48 hours, doctors may recommend medical treatment.
Possible approaches include:
Medications
Commonly prescribed drugs include:
- Chlorpromazine
- Baclofen
- Metoclopramide
- Gabapentin
These medications affect neurotransmitters involved in the hiccup reflex.
Treating underlying conditions
If an illness causes hiccups, treating the underlying disorder often resolves them.
Nerve stimulation or procedures
Rarely, severe cases require interventions such as:
- Phrenic nerve block
- Vagus nerve stimulation
- Surgical treatment of underlying lesions
Medical evaluation is recommended when hiccups last several days or interfere with daily life.
Why Common Remedies Sometimes Work
Many traditional hiccup remedies appear unusual, but they often work by affecting the same physiological pathways.
These remedies generally act through one of three mechanisms:
Increasing carbon dioxide levels
Methods such as breath holding or breathing into a paper bag increase carbon dioxide in the bloodstream. Higher carbon dioxide levels can suppress abnormal breathing reflexes.
Stimulating the vagus nerve
Swallowing sugar, drinking cold water, or pulling on the tongue stimulates nerves that influence breathing and the hiccup reflex.
Interrupting breathing patterns
Sudden changes in breathing rhythm can reset the reflex arc responsible for hiccups.
Because hiccups often stop spontaneously, it can be difficult to determine whether a particular remedy truly caused the episode to end.
Why Do Hiccups Occur? Scientific Theories
Despite being extremely common, the biological purpose of hiccups remains uncertain. There are several theories.
Evolutionary Reflex Theory
One hypothesis suggests that hiccups evolved from ancient breathing patterns in early vertebrates. Amphibians such as tadpoles use a similar reflex when switching between gill and lung breathing. The hiccup reflex may represent an evolutionary remnant of this early respiratory control system.
Infant Feeding Reflex
Another theory proposes that hiccups help infants coordinate breathing and swallowing during feeding. The reflex may help remove air from the stomach while allowing milk intake to continue.
This idea may explain why:
- Hiccups occur frequently in fetuses and newborns
- Episodes often happen during feeding
- The reflex becomes less common with age
Neural Development Theory
Some researchers believe hiccups may simply result from immature neural circuits that control breathing. As the nervous system develops and breathing patterns stabilize, hiccups become less frequent.
No single explanation fully accounts for all cases, so hiccups likely arise from multiple physiological mechanisms.
Risk Factors for Hiccups
Certain factors increase the likelihood of experiencing hiccups.
Lifestyle Factors
- Rapid eating or drinking
- Alcohol consumption
- Carbonated beverages
- Emotional stress or excitement
Medical Factors
- Gastrointestinal disorders
- Neurological diseases
- Chest surgery
- Anesthesia
- Certain medications
Men are slightly more likely than women to experience persistent hiccups.
Hiccups in Babies
Hiccups are extremely common in infants and often occur even before birth.
Fetal hiccups occur during pregnancy and can be detected as rhythmic movements in the womb.
In babies, hiccups usually result from:
- Feeding
- Swallowing air
- Immature nervous system control of breathing
Unlike adults, babies typically do not seem bothered by hiccups. Episodes usually stop on their own and rarely require treatment.
Parents can reduce hiccups by:
- Feeding infants slowly
- Burping them during feeding
- Keeping them upright after feeding
The frequency of hiccups decreases as the nervous system matures.
Hiccups in Other Animals
Hiccups occur in many mammals, including:
- Cats
- Dogs
- Horses
- Rats
In animals, the mechanism appears similar to that in humans and involves the diaphragm and respiratory nerves.
Young mammals experience hiccups more frequently than adults. Some researchers propose that hiccups may play a role in coordinating breathing and swallowing during early development.
Laboratory studies of animals have helped scientists understand the neural mechanisms behind the hiccup reflex.
Common Misconceptions
Hiccups occur because the body lacks oxygen.
Hiccups are not caused by low oxygen levels. They result from diaphragm spasms triggered by nerve signals.
Being scared is a reliable cure.
Startling someone may interrupt breathing patterns, but it does not reliably stop hiccups.
Drinking water upside down always works.
This method may help by changing breathing patterns or stimulating nerves, but results vary.
Hiccups only occur in humans.
Many animals experience hiccups due to similar respiratory anatomy.
Frequently Asked Questions (FAQs)
How long do hiccups usually last?
Most hiccups last a few minutes. Episodes lasting longer than 48 hours are considered persistent.
Can hiccups be dangerous?
Short episodes are harmless. Persistent hiccups may indicate an underlying medical problem and should be evaluated by a doctor.
Why do people get hiccups after drinking carbonated beverages?
Carbon dioxide gas expands the stomach, which can irritate the diaphragm and trigger the hiccup reflex.
Why do babies get hiccups so often?
Infants have developing nervous systems and often swallow air during feeding, both of which can trigger hiccups.
When should someone see a doctor for hiccups?
Medical evaluation is recommended if hiccups last longer than 48 hours, interfere with sleep or eating, or occur alongside other symptoms.
Summary
Hiccups are a common and usually harmless reflex involving the diaphragm and nervous system. Although most episodes stop quickly, the phenomenon reveals complex interactions between breathing muscles, nerves, and brainstem reflexes. Rare cases of persistent hiccups highlight how disruptions in these systems can affect even the simplest bodily functions.
References and Further Reading
- Chang, F. Y.; Lu, C. L. (2012). “Hiccup: Mystery, Nature and Treatment”. Journal of Neurogastroenterology and Motility. 18 (2): 123–130. doi:10.5056/jnm.2012.18.2.123
- Howes, Daniel (2012). “Hiccups: A new explanation for the mysterious reflex”. BioEssays. 34 (6): 451–453. doi:10.1002/bies.201100194
- Kahrilas, P. J.; Shi, G. (1997). “Why do we hiccup?”. Gut. 41 (5): 712–713. doi:10.1136/gut.41.5.712
- Lauterbach, E. C. (1999). “Hiccup and apparent myoclonus after hydrocodone: review of the opiate-related hiccup and myoclonus literature”. Clinical Neuropharmacology. 22 (2): 87–92. doi:10.1097/00002826-199903000-00004
- Moretto, Emilia N; Wee, Bee; Wiffen, Philip J; Murchison, Andrew G (2013). “Interventions for treating persistent and intractable hiccups in adults”. Cochrane Database of Systematic Reviews. 2019 (1) CD008768. doi:10.1002/14651858.cd008768.pub2