Nausea and Vomiting
Nausea is the unsettled, queasy feeling that often precedes vomiting. Together they are among the most common symptoms, arising from causes as varied as food poisoning, motion sickness, chemotherapy, pregnancy, and acute gastroenteritis, which spreads readily in high-heat, high-humidity conditions.
Key points
- Vomiting is triggered by a brainstem reflex that can be set off by gut irritation, inner-ear signals, circulating toxins, or certain medicines.
- Causes range from food poisoning and motion sickness to pregnancy, chemotherapy, and infections of the gut.
- Ondansetron blocks serotonin signals and is widely used for chemotherapy- and surgery-related nausea, while chlorpromazine targets dopamine pathways for more severe, persistent vomiting.
What triggers them
The vomiting reflex is controlled by the brainstem and can be activated by gut irritation, inner-ear disturbance, toxins in the bloodstream, certain medicines, or signals from the brain itself during anxiety or migraine. In travellers moving between countries, unfamiliar food and water are frequent culprits.
How they are treated
Mild cases often settle with rest, small sips of clear fluid, and bland food. When symptoms are severe, persistent, or tied to a specific cause such as chemotherapy or surgery, medicines that block nausea signals in the brain and gut are used. Ondansetron works by blocking serotonin receptors and is widely used for chemotherapy-related and post-operative nausea. Chlorpromazine acts on dopamine pathways and is used for severe or intractable vomiting, including cases linked to mental health conditions. Both are covered in the digestive health section of our catalogue.
Seek prompt medical attention if vomiting is accompanied by severe abdominal pain, blood in vomit, signs of dehydration, or if it follows a head injury.