Symptoms of the stomach flu include diarrhea, vomiting, fever, abdominal cramps and nausea, according to Mayo Clinic. Additionally, some people experience a headache and swollen lymph glands, adds WebMD.
These symptoms usually last one or two days but can last up to 10 days, states Mayo Clinic. Dehydration can occur in severe cases of the stomach flu; symptoms include sunken eyes, increased thirst and lightheadedness, reports WebMD. Contaminated food or water, viruses, bacteria or lactose intolerance cause the stomach flu, which people often confuse with influenza. Poor hygiene can also lead to the stomach flu. An individual who has been vomiting for more than 48 hours or vomiting blood requires medical attention, advises Mayo Clinic.