Understanding Food Allergy

An abnormal reaction of the IMMUNE SYSTEM to normally harmless foods. An allergic response involves two aspects of the immune system: circulating ANTIBODIES and specialized attack cells. Each branch of the immune system can react to foods as though they were foreign invaders. In contrast, other types of FOOD SENSITIVITY such as LACTOSE INTOLERANCE do not depend on antibody reactions, nor do they involve other aspects of the immune system.
Allergy patterns may change during a lifetime; old sensitivities may vanish, and new ones may appear according to the health of the immune system and to the amount of allergen exposure. Introducing solid foods before an infant’s DIGESTIVE
TRACT is fully developed carries an increased risk of the development of food allergies. Children are more likely to suffer from allergies than adults, though they often outgrow them. Individuals who have relatives with allergies are more prone to develop food allergies themselves. Food allergies are more likely to occur with inadequate nutrition, infections, and physical and emotional stress. Faulty DIGESTION and intestinal inflammation can allow food ALLERGENS to penetrate intestinal barriers and enter the bloodstream.
Depending on how food allergy is defined, estimates of the prevalence of food allergies range from 2 percent to 25 percent of the U.S. population. Opinion is also divided regarding the predominant form of food allergies. Those who consider food allergy an uncommon phenomenon focus on the readily observable, rapid systemic reactions to foods. These generate hay fever–like symptoms (immediate hypersensitivity). Other research indicates that typical food allergies are complex immune reactions resulting in delayed hypersensitivity. They frequently involve antibodies in the blood (IgG type), and symptoms develop over hours or days after consuming the problem food. This delay increases the difficulty in relating a specific food to sometimes vague symptoms.
The most common symptom of food allergy is FATIGUE. Other symptoms range from those typical of PREMENSTRUAL SYNDROME to HYPOGLYCEMIA, eczema, irritability, achy joints, puffy eyes with dark circles, or postnasal drip. Food allergies may produce asthma in the respiratory tract; in the brain, insomnia, mood changes, confusion, or fatigue; in the gastrointestinal tract, INDIGESTION, irritable colon, CONSTIPATION, or DIARRHEA.
A simple, proven method of coping with food allergies is abstinence. Avoiding the offending food for several days to several weeks may allow the immune system to return to normal. If symptoms recur when the questionable food is eaten again, that food is probably the culprit. ROTATION DIETS have been devised to minimize exposure to allergenic foods. Because allergy-restricted diets can be difficult to balance nutritionally, those who have multiple food allergies may wish to consult both a physician and a nutritionist. Individuals with food allergies often need to find substitutes for common foods. A wide variety of food allergy cookbooks are now available to help plan delicious, nutritious meals.