An upset stomach after eating eggs can be caused by having an allergy to eggs. Common symptoms of an egg allergy include cramps, nausea, vomiting, skin inflammation or hives, nasal congestion, coughing, wheezing and shortness of breath, according to Mayo Clinic. In severe cases, egg allergies can lead to anaphylaxis, which typically causes rapid pulse, constriction of the airways and severe drop in blood pressure.
To avoid having an upset stomach or other symptoms caused by an egg allergy, it is important to avoid eating eggs and check food labels to ensure products do not contain any eggs. When someone has an egg allergy, it is because their immune system has become sensitized to the proteins found in eggs. Many children with egg allergies grow out of the allergy, but some have it all of their lives.