Reactions to a food you’ve eaten are relatively common. While many people assume that this is a sign of a food allergy, in fact, most reactions are caused by a food intolerance, not a true food allergy. Many of the symptoms can be the same, leading to confusion, but the causes are actually different.
A true food allergy occurs when the immune system attacks a protein in the food as a foreign substance. This can cause wide-ranging symptoms that may even be life-threatening. In contrast, a food intolerance tends to be less serious, with symptoms mainly affecting the digestive system. Symptoms of a food intolerance include nausea, vomiting, stomach pain, gas, bloating, diarrhea, and heartburn.
There are several causes of food intolerance. One is the absence of an enzyme that is needed to fully digest a component of the food, such as lactose intolerance. Irritable bowel syndrome and food poisoning caused by bacteria in the food are also considered food intolerance. Some food intolerances are caused by a sensitivity to additives like artificial colors or sulfites used to preserve canned or dried foods. Some doctors also consider Celiac disease – triggered by eating gluten contained in wheat and other grains — to be a food intolerance, though it does have some of the features of a true food allergy.
If you experience a reaction after eating certain foods, see your doctor for testing to determine whether you have an allergy or food intolerance. If you have a food intolerance, you may be able to eat small quantities of the food, or may not experience a reaction until several hours after eating. There may also be steps you can take to prevent a reaction, such as taking lactase pills to aid digestion if you have lactose intolerance.