Food allergies: causes and symptoms

It is estimated that almost one-third of people say they, or a family member, have a food allergy. But in fact, only two to eight percent of children, and one to two percent of adults, have clinically proven allergic reactions to food. The reason for this discrepancy is that we often fail to discriminate between food allergies and food intolerances.  The following guidelines will tell you more.

True food allergies involve the body's immune system, whereas a food intolerance originates in the gastro­intestinal system and involves an inability to digest or absorb certain substances.

Doctors do not completely understand why so many people have allergies, though heredity is an important consideration. If both parents have allergies, their children will almost always have them as well, although the symptoms and allergens may be quite different.

Food allergies in infants and children however, tend to lessen as they grow, and the problem may disappear by adulthood. There is no doubt that breastfeeding and the delayed introduction of solid foods reduces the chance of food allergies.

Allergies develop in stages. When the immune system first encounters an allergen (or antigen) — a substance that it mistakenly sees as a harmful ­foreign invader — it signals specialized cells to make antibodies, or immunoglobulins, against it. There is no allergic reaction in that first exposure; however, if the substance again enters the body, the antibodies programmed to mount an attack against it will go into action.

In some instances, the response will not produce symptoms; but the stage will have been set for a future antigen-antibody reaction and an allergic response.

• There are many symptoms of food allergies, including nausea, vomiting, diarrhea, constipation, indigestion, headaches, skin rashes or hives, itching, shortness of breath (including asthma attacks) and, in severe cases, widespread swelling of the skin and mucous membranes.
• Swelling in the mouth or throat is potentially fatal because it can block the airways to the lungs.
• In the most severe cases, anaphylactic shock — a life-threatening collapse of the respiratory and circulatory system — may develop.
• Allergens usually provoke the same symptoms each time, but many factors affect intensity, including how much of the offending food was eaten and how it was prepared.
• Some people can tolerate small amounts of an offending food; others are so hypersensitive that they react to even a minute trace.