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A food allergy is a reaction by the body's immune system to a substance or ingredient in food - usually a protein. According to the National Institutes of Health, approximately five million Americans (5-8 percent of children and 1-2 percent of adults) have a true food allergy.

Eight major food allergens account for 90 percent of all allergic reactions: milk, eggs, peanuts, tree nuts (such as walnuts or almonds), soy, wheat, fish and shellfish. Children are most commonly affected by reactions to milk and eggs. Chocolate is an uncommon food allergen.

Some people, health professionals included, incorrectly confuse the terms "food sensitivity" and "food allergy." A food intolerance or sensitivity is a reproducible adverse reaction, not psychologically based, which includes enzyme deficiencies, pharmacological effects, non-immunologic histamine-releasing effects, and direct irritation. A food allergy or hypersensitivity is a form of food intolerance that includes an abnormal immunologic reaction mediated by antibody and/or T lymphocytes.

The only completely objective test for confirming a food allergy is the double-blind placebo-controlled food challenge (DBPCFC). The most prevalent food allergens confirmed by DBPCFC are eggs, milk, soy, fish, peanuts, tree nuts, and wheat.

Patients' perceptions and physicians' diagnoses of food intolerance are not always accurate; fewer than half of patients with histories of adverse reactions to food can be confirmed by means of objective testing. In the case of chocolate, Fries was rarely able to confirm a parent's suspicions of a child's allergies.

According to Fries, few scientific publications relate chocolate to allergy. Fries reported positive skin test response to the cocoa bean in about two-thirds of allergy patients. However, test results were not related to clinical symptoms. Maslansky and Wein questioned 500 allergy patients regarding their tolerance of chocolate. Although 81 said they suffered from chocolate allergy, only 10 had the requisite reproducible symptoms for inclusion in the double-blind study. Eight of these patients were challenged and only three had a reaction. Of these three, only one had both symptoms and a positive skin test.

In another study, 20 patients with a history of "allergic" reactions to chocolate were fed either placebo or cocoa in a double-blind manner. The cocoa ingested approximated the amount in an average size chocolate bar. Participants also were fed a chocolate bar at another point in the study. The authors concluded that only one participant probably was allergic to chocolate. Likewise, other studies rarely confirmed suspected reactions to chocolate by oral challenge.

Dermal antigen tests to determine allergic response to foods can sometimes be misleading. Problems with dermal antigen testing include a large number of clinically insignificant positive tests, cross-reactivity among foods from common genetic families, and use of an improper antigen (i.e., cocoa bean instead of processed cocoa). The cocoa bean goes through several procedures (e.g., fermentation, roasting, grinding, conching) before it can be consumed as chocolate. Thus, a higher incidence of positive cutaneous tests may result than the incidence of clinical reactions to other ingredients or to the products of its digestion.

Chocolate candies may contain other ingredients that can elicit allergic reactions, including such common foods as milk, soy lecithin, gluten, peanuts and tree nuts. This highlights the importance of label reading by people who may be sensitive to these ingredients.

The diagnosis of chocolate reactions should be based on reliable studies, including food elimination and food challenge tests.