Nausea is caused by a variety of factors affecting different systems in the body. Common causes include:

• Gastrointestinal issues: infections (like stomach flu or gastroenteritis), food poisoning, gastritis, ulcers, gallbladder disease, and gastroesophageal reflux disease (GERD) can cause nausea by irritating or disrupting normal digestive processes

• Medications and toxins: certain drugs, including chemotherapy, and ingestion of toxic substances can trigger nausea

• Motion sickness: disturbances in the vestibular system of the inner ear during travel or movement can cause nausea

• Pregnancy: especially in the first trimester, nausea (morning sickness) is very common

• Psychological factors: stress, anxiety, fear, and emotional distress can provoke nausea

• Other medical conditions: pain (such as from pancreatitis or kidney stones), infections beyond the gut (like flu or COVID-19), migraines, heart problems, and neurological issues can also cause nausea

Physiologically, nausea results from activation of several pathways including the central nervous system, chemoreceptor trigger zone in the brain, vestibular system, and peripheral receptors in the gastrointestinal tract and other organs. These pathways send signals to the brainstem, which coordinates the sensation of nausea and related motor responses like vomiting

. In summary, nausea is a symptom with many possible causes ranging from digestive disorders and infections to medications, motion sickness, pregnancy, and psychological factors. It involves complex interactions between the brain and body systems responding to various triggers