Vomiting (also known as emesis, puking and throwing up)[a] is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose.

[1] Vomiting can be the result of ailments like food poisoning, gastroenteritis, pregnancy, motion sickness, or hangover; or it can be an after effect of diseases such as brain tumors, elevated intracranial pressure, or overexposure to ionizing radiation.

[4] Prolonged and excessive vomiting depletes the body of water (dehydration), and may alter the electrolyte status.

Gastric vomiting leads to the loss of acid (protons)[clarification needed] and chloride directly.

Combined with the resulting alkaline tide, this leads to hypochloremic metabolic alkalosis (low chloride levels together with high HCO−3 and CO2 and increased blood pH) and often hypokalemia (potassium depletion).

Receptors on the floor of the fourth ventricle of the brain represent a chemoreceptor trigger zone, known as the area postrema, stimulation of which can lead to vomiting.

The pressure is then suddenly released when the upper esophageal sphincter relaxes resulting in the expulsion of gastric contents.

Fecal vomiting is often a consequence of intestinal obstruction or a gastrocolic fistula and is treated as a warning sign of this potentially serious problem (signum mali ominis).

[citation needed] If the vomiting reflex continues for an extended period with no appreciable vomitus, the condition is known as non-productive emesis or "dry heaves", which can be painful and debilitating.

Some emetics, such as ipecac, fall into both categories; they initially act directly on the stomach, while their further and more vigorous effect occurs by stimulation of the medullary center.

This phenomenon has been touched on in popular culture: notorious instances appear in the films Monty Python's The Meaning of Life (1983) and Stand by Me (1986).

However, people who experience "la purga" after drinking ayahuasca, in general, regard the practise as both a physical and spiritual cleanse and often come to welcome it.

[42] It has been suggested that the consistent emetic effects of ayahuasca—in addition to its many other therapeutic properties—was of medicinal benefit to indigenous peoples of the Amazon, in helping to clear parasites from the gastrointestinal system.

[citation needed] An online study of people's responses to "horrible sounds" found vomiting "the most disgusting".

Professor Trevor Cox of the University of Salford's Acoustic Research Centre said, "We are pre-programmed to be repulsed by horrible things such as vomiting, as it is fundamental to staying alive to avoid nasty stuff."

It is thought that disgust is triggered by the sound of vomiting to protect those nearby from possibly diseased food.