Nausea is an uncomfortable sensation in the stomach, often described as feeling “sick to your stomach,” that can precede vomiting but does not always lead to it. It is a common symptom, indicating a disturbance within the body rather than a disease itself. This sensation can arise from numerous sources.
The Body’s Nausea Control Center
Nausea involves specific brain areas that act as control centers. A key region is the chemoreceptor trigger zone (CTZ), located in the medulla oblongata. It is sensitive to chemicals in the blood because it lies outside the blood-brain barrier, allowing it to detect circulating toxins or medications that might induce nausea.
The CTZ then communicates with the vomiting center, also in the medulla, which coordinates the physical act of vomiting. Signals can originate from the gastrointestinal tract via the vagus nerve, the inner ear’s vestibular system (responsible for balance), and higher brain centers influenced by thoughts or emotions. These signals are integrated by the brain, leading to the sensation of nausea.
Digestive System Contributors
Many common causes of nausea originate within the gastrointestinal tract, often involving irritation or disruption of normal digestive function. Food poisoning, caused by bacterial or viral infections, can irritate the stomach and intestinal lining, resulting in nausea. Viral gastroenteritis, or “stomach flu,” similarly inflames the digestive tract and frequently causes nausea and vomiting.
Conditions like acid reflux (GERD) occur when stomach acid flows back into the esophagus, irritating its lining and triggering nausea. Indigestion, often from overeating, can upset the stomach. Digestive disorders such as irritable bowel syndrome (IBS) can also contribute to nausea, potentially due to altered gut-brain signaling. Gastroparesis, where stomach muscles do not properly move food into the small intestine, causes delayed emptying and frequently results in nausea and vomiting.
Nausea from Other Body Systems
Nausea can also arise from sources outside the digestive system, triggered by various bodily processes or external factors. Motion sickness occurs when visual input conflicts with signals from the inner ear’s vestibular system, which senses movement and balance. Hormonal fluctuations contribute to nausea, notably in early pregnancy, where increased levels of hormones like human chorionic gonadotropin (hCG) cause “morning sickness.” Menstrual cycles and other hormonal imbalances can also cause nausea.
Many medications list nausea as a side effect, including chemotherapy drugs, antibiotics, and certain pain relievers. These can stimulate the brain’s nausea centers or irritate the gastrointestinal tract. Neurological conditions such as migraines often involve nausea alongside headache pain. Head injuries or other brain conditions can also trigger this symptom.
Stress and anxiety activate the body’s “fight or flight” response, releasing hormones that can slow digestion and increase gut sensitivity, causing nausea through the gut-brain connection. Systemic illnesses like kidney disease, liver disease, diabetes, and severe infections can also induce nausea due to metabolic changes or the body’s inflammatory response.
When to Seek Medical Guidance
While nausea is often temporary and mild, certain indicators suggest a more serious underlying condition requiring medical attention. Persistent nausea or vomiting lasting over 48 hours in adults, or shorter durations in children and infants, warrants evaluation. Seek immediate medical care if nausea is accompanied by severe abdominal pain, high fever, a stiff neck, confusion, or severe headache.
Other concerning symptoms include signs of dehydration like excessive thirst, dry mouth, infrequent urination, or dizziness. Vomit containing blood, resembling coffee grounds, or appearing green, as well as unexplained weight loss, are also red flags. Early consultation with a healthcare provider ensures appropriate assessment and treatment for the underlying cause.