A sour stomach from protein indigestion is commonly the result of a food allergy or food intolerance. Food allergies are caused by a reaction of the immune system, while food intolerances are the result of the inability to digest certain proteins found in foods. Your doctor may recommend that you participate in an elimination diet to identify which foods are causing the sour stomach. All digestive symptoms that persist for more than three days need to be discussed with your doctor.
Food Allergy
A food allergy can cause a sour stomach within minutes after eating certain food proteins. Food allergies are caused by a malfunction of the immune system that causes digestive complications. MayoClinic.com states that the most common foods that trigger an allergic reaction include soy, wheat, dairy, fish, peanuts, tree nuts and eggs. It's the proteins in these foods that the immune system mistakes for harmful substances, when in reality the proteins are harmless. A food allergy will cause other symptoms aside from a sour stomach. Common symptoms include hives, skin rashes, nasal congestion, shortness of breath and chest pain.
Protein Intolerance
Food protein intolerances are a common cause of a sour stomach. The main difference between a food allergy and protein intolerance is the cause. Food allergy symptoms are caused by an immune system reaction, while food protein intolerances are the result of the inability to digest proteins found in food. For example, if you're intolerant of milk proteins, your digestive system doesn't create the appropriate enzymes needed to digest the proteins. When this occurs, the proteins remain undigested, causing inflammation and irritation in the lining of your digestive system. This can lead to nausea, vomiting and diarrhea.
Elimination 'Diet
Use an elimination to identify which foods are causing adverse reactions in your stomach. The University of Wisconsin states that an elimination diet is intended to narrow down which foods are triggering your symptoms, but is not intended to diagnose a condition. Remove the foods from your diet that you suspect are triggering your upset stomach for two weeks. At the end of the two weeks, reintroduce one food at a time back into your diet. Keep a detailed record of what you food you eat, when you ate it, how much of it you ate and how it affects your body. Report your findings to your doctor.
Treatment
Both food allergies and food intolerances are treated by identifying the foods that are triggering your symptoms and removing them from your diet. Permanently eliminating certain foods may be more difficult than you think. For example, milk is used in most baked goods and is found in deli meats, sauces and non-dairy creamers.
