Food Allergy

• What is the importance of food allergy?
• How do allergic reactions to food work?
• What are the symptoms of food allergy?
• Do infants and children have problems with food allergy?
• What are the most common food allergies?
• What is cross-reactivity?
• What is exercise-induced food allergy?
• What conditions have mistakenly been attributed to food allergy?
• What is the differential diagnosis of food allergy?
• How is food allergy diagnosed?
• What diagnostic techniques for food allergy are unproven?
• How is food allergy treated?
• What treatments for food allergy are controversial?
• Food Allergy At A Glance

Food Allergy Myths Medical Author: Melissa Conrad Stöppler, MD Medical Editor: Jay W. Marks, MD Food allergies are often misunderstood, even though societal recognition of, and education about, the condition is increasing. See if you have heard – or believed – any of the following myths about food allergies: "You're "allergic" to any food that gives you problems." This statement is false, since there are several problems that can arise after eating specific foods, the majority of which are unrelated to allergy. True allergies to foods are immunologic reactions involving the class of immunoglobulins (proteins that assist in the body's immune response) known as immunoglobulin (Ig) E. Other kinds of reactions to foods that are not food allergies include food intolerances (such as lactose or milk intolerance ), food poisoning, and toxic reactions. The prevalence of food allergy in the population is much lower than the prevalence of adverse reactions to foods. It is estimated that true food allergies occur in 2-5% of the population. "All food allergies in children resolve as they get older." As they grow older, some children may tolerate foods that previously caused allergic reactions. This is more likely to happen in the case of allergies to milk, eggs, and wheat, in which the severity of reactions (or symptoms) may decrease by late childhood. It is not clear in all cases, however, if the improved symptoms are an indication that the allergy has disappeared. For example, in wheat allergy (celiac disease) symptoms may improve, but a mild allergic reaction continues in the intestine, and symptoms and signs of the allergy may recur in later years. On the other hand, milk allergy appears to truly disappear as children grow older. Find out about peanut and fruit allergies » Top Searched Food Allergy Terms: milk, wheat, peanut, fruit, nut, blood test, anaphylaxis, soy

What is the importance of food allergy?

Food allergy or food intolerance affects nearly everyone at some point. When people have an unpleasant reaction to something they ate, they often think that they have an allergy to the food. In fact, one out of three people say that some member of their family has an allergy to food that has necessitated a change in their diet. Actually, however, only about 1% of adults and 3% of children have clinically proven allergic reactions to food.

This difference between the prevalence of clinically proven food allergy and the public's perception of the problem is due primarily to misinterpreting food intolerance as food allergy. Food allergy is an abnormal response to food that is triggered by a specific reaction in the immune system and expressed by certain, often characteristic, symptoms. Food intolerance also is an abnormal response to food, and its symptoms can resemble those of food allergy. Food intolerance, however, is far more prevalent, occurs in a variety of diseases, and is triggered by several different mechanisms that are distinct from the immunological reaction responsible for food allergy.

People who have food allergies must identify and prevent them because, although usually mild and not severe, these reactions can cause devastating illness and, in rare instances, be fatal.

How do allergic reactions to food work?

The allergens in food are those components that are responsible for an allergic reaction. They are proteins that usually resist the heat of cooking, the acid in the stomach, and the intestinal digestive enzymes. As a result, the allergens survive to cross the gastrointestinal lining, enter the bloodstream, and go to target organs, causing allergic reactions throughout the body. The mechanism of food allergy involves the immune system and heredity.

Immune system: An allergic reaction to food involves two components of the immune system. One component is a type of protein, an antibody called immunoglobulin E (IgE), which circulates through the blood. The other is the mast cell, a specialized cell that is in all tissues of the body. The mast cell is especially common, however, in areas of the body that are typical sites of allergic reactions, including the nose and throat, lungs, skin, and gastrointestinal tract.

Heredity: The tendency of an individual to produce IgE against something seemingly as innocuous as food appears to be inherited. Generally, allergic people come from families in which allergies are common-not necessarily to food, but perhaps allergies to pollen, fur, feathers, or drugs. Thus, a person with two allergic parents is more likely to develop food allergies than someone with one allergic parent.

Mechanism: Food allergy is a hypersensitivity reaction, meaning that before an allergic reaction to an allergen in food can occur, a person needs to have been exposed previously, that is, sensitized, to the food. At the initial exposure, the allergen stimulates lymphocytes (specialized white blood cells) to produce the IgE antibody that is specific for the allergen. This IgE then is released and attaches to the surface of the mast cells in different tissues of the body. The next time the person eats that food, its allergen hones in on the specific IgE antibody on the surface of the mast cells and prompts the cells to release chemicals such as histamine. Depending upon the tissue in which they are released, these chemicals cause the various symptoms of food allergy.

From the Doctors at MedicineNet.com

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