A negative reaction to food is often erroneously called a food allergy.
In many cases it is caused by other agents, such as a microbial food poisoning, a psychological aversion to a food or intolerance to a certain ingredient (dye and/or preservative) in the food.
A food allergy is a specific form of intolerance to food that activates the immune system. An allergen (a protein present in the food that is normally absolutely harmless to most people) triggers a chain reaction in the immune system, including the production of antibodies. Antibodies cause the release of substances from the body, such as histamines, which produce a variety of symptoms: itching, runny nose, cough, shortness of breath, diarrhea, vomiting.
Food allergies are often diagnosed in the first years of life. The most common food allergens are cow’s milk, eggs, wheat, peanuts and shellfish.
Food intolerance affects the metabolism, not the immune system. A typical example is lactose intolerance: people affected have a deficiency of lactase, the digestive enzyme that breaks down milk sugar. Intolerance may cause allergy-like symptoms, such as nausea, diarrhea and stomach cramps.
In food intolerance, the most frequently involved additives are benzoates, sulphites and acetylsalicylic acid.
This intolerance is an intestinal disorder that occurs when the body cannot tolerate gluten (a protein found in wheat).
Occurrence of this disease, commonly known as celiac disease, has been underestimated, but it is believed that about 1in 100 people in Europe suffers from celiac disease.
This permanent intolerance can be diagnosed at any age. Symptoms include diarrhea, weight loss, irritability, and abdominal cramps.
Currently, the only possible help for celiac patients is a gluten-free diet. By excluding this substance from the diet, the intestine gradually repairs itself and symptoms disappear.