Vomiting, or emesis, is the forceful expulsion of stomach or upper gastrointestinal contents through the mouth. It is a coordinated protective reflex involving the brainstem, gastrointestinal tract, diaphragm, abdominal muscles, respiratory muscles and oesophageal sphincter mechanisms. Vomiting differs from regurgitation, in which gastric contents passively return into the mouth without the characteristic retching and forceful muscular sequence. It also differs from reflux, which describes movement of stomach contents into the oesophagus and may occur without expulsion. Vomiting can be a protective response to toxins or gastrointestinal irritation, but persistent or severe vomiting can itself cause substantial physiological harm.
The motor process of Vomiting usually involves a preceding phase of nausea or retching, although these are not obligatory. The brainstem integrates signals from the gastrointestinal tract, vestibular system, higher brain centres and circulating chemicals. Coordinated contraction of the diaphragm and abdominal musculature increases intra-abdominal pressure while changes in the stomach and oesophageal sphincters permit gastrointestinal contents to move upwards. The airway is protected through coordinated respiratory and laryngeal responses. The chemoreceptor trigger zone and associated brainstem networks are particularly important in detecting circulating substances that may provoke emesis.
Common causes of Vomiting include gastroenteritis, food poisoning, medication effects, excessive alcohol intake, migraine, pregnancy, motion sickness and postoperative states. More serious causes include intestinal obstruction, appendicitis, intracranial disease, metabolic disorders, pancreatitis, severe infection and toxic ingestion. In children, the differential diagnosis changes with age, and projectile or bilious vomiting can be clinically significant. The colour and contents of vomit can provide clues: green or bile-stained material may indicate duodenal contents and can be concerning for obstruction, while blood can indicate upper gastrointestinal bleeding. Interpretation always depends on the complete clinical picture.
Repeated Vomiting can cause dehydration and disturbances in electrolytes and acid-base balance. Loss of gastric hydrochloric acid can contribute to metabolic alkalosis, while prolonged inability to eat can alter glucose and nutritional status. Severe retching can damage the oesophageal or gastric mucosa and, in some cases, produce a Mallory-Weiss tear that causes bleeding. Aspiration of vomited material into the lungs can lead to chemical pneumonitis or aspiration pneumonia. These complications explain why the severity and frequency of vomiting matter even when the underlying illness is relatively short-lived.
Treatment of Vomiting focuses on the underlying cause and prevention of complications. Oral rehydration can be effective when the person can retain small amounts of fluid, while intravenous fluids may be necessary for significant dehydration or inability to drink. Antiemetic medicines can act on serotonin, dopamine, histamine, acetylcholine or neurokinin pathways, with different drugs suited to different causes. In mechanical obstruction, simply suppressing vomiting is not sufficient because the obstruction itself requires assessment and treatment. Medication choice must consider age, pregnancy, cardiac risk, neurological effects and interactions.
Vomiting can be a particularly important symptom in intestinal obstruction. Obstruction prevents normal forward passage of gastrointestinal contents and can lead to abdominal distension, cramping pain, inability to pass stool or gas and progressive vomiting. Persistent vomiting associated with severe abdominal pain, distension or inability to retain fluids therefore warrants urgent medical evaluation. Similarly, vomiting accompanied by severe headache, altered consciousness, neurological deficits or recent head injury can indicate an intracranial process rather than a gastrointestinal disorder. Blood in vomit, coffee-ground material, green vomit in certain contexts and signs of severe dehydration are other important warning features.
Diagnosis is guided by chronology, triggers, frequency, associated symptoms and physical examination. Clinicians may assess hydration, abdominal tenderness or distension, neurological findings and signs of infection. Blood tests can identify electrolyte abnormalities, kidney dysfunction or metabolic disturbances, while imaging can investigate obstruction, inflammation or other structural disease. Endoscopy may be required when upper gastrointestinal bleeding or persistent unexplained vomiting is suspected. The history of recent medication changes, surgery, travel, food exposure, alcohol use and possible pregnancy can be diagnostically valuable.
Vomiting has evolutionary and physiological value as a mechanism for expelling potentially harmful substances, but it is not inherently beneficial in every situation. Inducing vomiting after suspected poisoning is generally unsafe because some substances can damage the oesophagus or be aspirated into the lungs during emesis. Vomiting should also be distinguished from coughing up blood, which originates in the respiratory tract, and from regurgitation associated with swallowing or oesophageal disorders. Its significance ranges from a brief symptom of self-limiting illness to a manifestation of life-threatening disease, so duration, contents, associated symptoms and hydration status are essential to interpretation.
