Food allergies occur because of a hypersensitivity and abnormal reaction to certain proteins in the food. Food intolerances, though not as serious as an allergy, also cause an abnormal reaction to food. Some foods that people are commonly allergic to include peanuts, wheat, strawberries and more. Also common is gluten intolerance and lactose intolerance. Learn more about how to diagnose a food allergy, living with an allergy, medication, anaphylactic shock and other issues surrounding food allergies.