Feeling nauseous when eating fish may be related to a number of factors, including allergies, unhygienic diet, food preparation, and digestive disorders. 1. Allergy: If you are allergic to foods such as seafood, you may experience a severe allergic reaction when eating fish, which can lead to nausea, vomiting and other symptoms. 2. Unhygienic diet: If you eat spoiled fish, it may cause gastrointestinal reactions or even toxic reactions and other symptoms such as nausea and vomiting. 3. Food cooking: after putting too much spicy and stimulating seasoning into fish when making fish, such as spicy fish. If the function of gastrointestinal tract is not good, it is easy to cause nausea and other symptoms after eating. 4. Digestive system diseases: most of the patients with acute hepatitis, acute cholecystitis and pancreatitis and other diseases can appear abdominal pain, nausea, vomiting, anorexia of greasy food and other symptoms, nausea may also occur after eating fish. It is recommended to go to the hospital in a timely manner to clarify the cause of the disease and then carry out targeted treatment.