Vomiting is caused by a signal in the brain. It can be triggered by nausea, which may result from a variety of stimuli such as motions, smells, tastes, infections and emotions. In addition, overindulgence in a particular food or alcohol may induce nausea or vomiting.

There are many possible causes of nausea and vomiting. They include:

• Gastrointestinal (GI) disorders. Many disorders of the stomach and intestines cause nausea and vomiting. Some of the most common disorders include:
  
  
  • Infectious disease. Viral gastroenteritis is an infection of the stomach or intestines by a particular virus. Foodborne illnesses are acute GI infections caused by eating food that contains harmful bacteria, toxins, viruses or parasites.
    
    
  • Gastroparesis. A condition in which food or liquid passes too slowly from the stomach into the small intestine. This is common in people who have had diabetes for many years.
    
    
    
    
    
  • Pancreatitis. Inflammation or irritation of the pancreas, often due to gallstones or alcohol abuse.
    
    
    
    
    
  • Intestinal blockage. This can be due to peptic ulcers (an open sore, or ulcer, in the lining of the esophagus, stomach or duodenum) or inflammatory diseases, such as Crohn's disease (a type of inflammatory bowel disease in which the large intestine or small intestine is inflamed over a long period of time).
    
    
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  • Gallstones. Hard, stonelike masses formed from substances in bile such as cholesterol or bilirubin that develop in the gallbladder or bile ducts.
    
    
• Medications. Many medications can cause nausea and vomiting as side effects. The best known are those used to treat cancer. Narcotics, antibiotics and the pain relievers known as nonsteroidal anti-inflammatory drugs (NSAIDs) may also cause nausea or vomiting. Some people experience nausea or vomiting during recovery from surgery, as a side effect of general anesthesia. In addition, research suggests that nausea and vomiting may result from the use of illegal drugs (e.g., cocaine) as well.
  
  
• Disorders of the central nervous system (CNS). Nausea and vomiting are sometimes related to serious CNS conditions, such as brain tumors and increased cranial pressure. However, they are more commonly associated with the following:
  
• • Motion sickness. Illness caused by sudden direction changes or disorientation.
    
    
  • Migraine headaches. A severe form of headache that involves the blood vessels, nerves and chemicals in the brain.
    
    
  • Meningitis. An infection in the lining in the brain.
    
    
• Systemic conditions. Problems or changes in other body systems may cause nausea or vomiting. Some of the most common include pregnancy, kidney failure or a heart attack.
  
  
• Psychiatric conditions. Eating disorders such as bulimia nervosa commonly involve vomiting. People with this disorder binge eat and then induce vomiting to purge the excess food from their body. Anxiety and depressive disorders may sometimes include nausea or vomiting., among other symptoms. Nausea may also be a symptom of a concussion (temporary brain injury caused by a blow to the head).
  
  
• Cyclic vomiting syndrome. Severe, repeated attacks of vomiting, nausea and physical exhaustion that begin and end suddenly with no apparent cause.