What is vomiting?

Vomiting expels some of the contents of the stomach through the mouth. This is a defence mechanism in case we swallow toxic substances or spoiled food. Vomiting can be triggered, but it is usually a reflex. When we vomit, an anti-peristaltic movement pushes food in the opposite direction to the peristaltic waves that normally move food down through the digestive tract.

A reflex closes the glottis to prevent vomit from going into the trachea and the lungs. Unlike vomiting, regurgitation is a passive movement of the contents of the stomach back up towards the back of the throat or the oral cavity.

What causes vomiting?

Food poisoning or some diseases of the digestive tract, such as a stomach ulcer or gastroenteritis (an inflammation of the wall of the digestive tract) can cause vomiting. Motion sickness or vertigo are related to the balance function of the ears and can also cause nausea and vomiting, as can the side effects of some types of medication.