While many people have adverse reactions to certain foods, true food allergies triggered by the immune system are relatively uncommon, affecting about 2% of adults and 6% of children. Symptoms of food allergies can include tingling in the mouth, hives, swelling of the lips, face, tongue, and throat, wheezing or breathing difficulties, dizziness, or fainting.
Food intolerance is different from a food allergy as it does not involve the immune system. Lactose intolerance is an example of this. Some people are lactose intolerant because they lack the enzyme lactase, which is needed to digest lactose found in milk and other dairy products. When lactose is not properly digested, it can cause abdominal pain, diarrhea, and bloating.
If you have a food allergy, even a tiny amount of the food can trigger a severe allergic reaction. In contrast, if you have a food intolerance, you can typically consume small amounts of the food without any adverse reaction.