Yes onions can upset some peoples stomachs because onions are high in fructans which causes digestive issues in some people and even bloating.
Some people also have an intolerance to onions and if so they may need to avoid eating onions if it continues to upset their stomachs.
Some signs that you may be intolerant to onions are.
- Tingling or itching in the mouth.
- Hives, itching or eczema.
- Swelling of the lips, face, tongue and throat or other parts of the body.
- Wheezing, nasal congestion or trouble breathing.
- Abdominal pain, diarrhea, nausea or vomiting.
- Dizziness, lightheadedness or fainting.