Allergenic Foods

Virtually all food allergens are proteins, although only a small percentage of the many proteins in foods are allergens. Any food that contains protein has the potential to cause allergic reactions in some individuals. However, a few foods or food groups are known to cause allergies on a more frequent basis than other foods. At a 1995 consultation on food allergies sponsored by the Food and Agriculture Organization, a group of international experts confirmed that peanuts, soybeans, crustacea, fish, cow’s milk, eggs, tree nuts, and wheat are the most common allergenic foods. These foods are responsible for more than 90% of serious allergic reactions to foods. Allergies to certain fresh fruits and vegetables are also rather common, but the allergens tend to be labile to processing and cooking and the symptoms are mild and confined primarily to the oropharyngeal area. The prevalence of allergic sensitivities to specific foods varies from one country to another depending on the frequency with which the food is eaten in that country and the typical age at its introduction into the diet. For example, peanuts are a much more frequent cause of food allergies in the United States than in most other countries. Americans eat peanuts more often and introduce peanut butter into the diet of children at an early age. The Japanese probably experience more soybean and rice allergies than some other cultures because of the frequency of these two foods in the Japanese diet. Scandinavians have a high incidence of codfish allergy for similar reasons. Table 1 provides a listing of the most common allergenic foods and food groups compiled from a thorough search of the medical literature. Table 2 provides a listing of the less common allergenic foods. Only some of the foods listed in this table have been documented to cause severe, life-threatening allergic reactions. Citations are provided to studies and/or case reports that document the allergenicity of those particular foods. The absence of a particular food on this list may not mean that it is nonallergenic but may indicate that its allergenicity has not been documented. Conversely, the presence of a specific food on the list merely indicates that it has been listed in one or more reports as a cause of food allergy and does not indicate the prevalence or potential as an allergenic food

An Evaluation of the Sensitivity of Subjects with Peanut Allergy to Very Low Doses of Peanut Protein: A Randomized, Double-Blind, Placebo-Controlled Food Challenge Study

The minimum dose of food protein to which subjects with food allergy have reacted in double-blind, placebo-controlled food challenges is between 50 and 100 mg. However, subjects with peanut allergy often report severe reactions after minimal contact with peanuts, even through intact skin. Objective: We sought to determine whether adults previously proven by challenge to be allergic to peanut react to very low doses of peanut protein. Methods: We used a randomized, double-blind, placebo-controlled food challenge of 14 subjects allergic to peanuts with doses of peanut ranging from 10 μg to 50 mg, administered in the form of a commercially available peanut flour. Results: One subject had a systemic reaction to 5 mg of peanut protein, and two subjects had mild objective reactions to 2 mg and 50 mg of peanut protein, respectively. Five subjects had mild subjective reactions (1 to 5 mg and 4 to 50 mg). All subjects with convincing objective reactions had short-lived subjective reactions to preceding doses, as low as 100 μg in two cases. Five subjects did not react to any dose up to 50 mg. Conclusion: Even in a group of well-characterized, highly sensitive subjects with peanut allergy, the threshold dose of peanut protein varies. As little as 100 μg of peanut protein provokes symptoms in some subjects with peanut allergy

Factors affecting the determination of threshold doses for allergenic foods: How much is too much?

Background: Ingestion of small amounts of an offending food can elicit adverse reactions in individuals with IgE-mediated food allergies. The threshold dose for provocation of such reactions is often considered to be zero. However, because of various practical limitations in food production and processing, foods may occasionally contain trace residues of the offending food. Are these very low, residual quantities hazardous to allergic consumers? How much of the offending food is too much? Very little quantitative information exists to allow any risk assessments to be conducted by the food industry. Objective: We sought to determine whether the quality and quantity of existing clinical data on threshold doses for commonly allergenic foods were sufficient to allow consensus to be reached on establishment of threshold doses for specific foods. Methods: In September 1999,12 clinical allergists and other interested parties were invited to participate in a roundtable conference to share existing data on threshold doses and to discuss clinical approaches that would allow the acquisition of that information. Results: Considerable data were identified in clinical files relating to the threshold doses for peanut, cows\u27 milk, and egg; limited data were available for other foods, such as fish and mustard. Conclusions: Because these data were often obtained by means of different protocols, the estimation of a threshold dose was very difficult. Development of a standardized protocol for clinical experiments to allow determination of the threshold dose is needed

Assessing genetically modified crops to minimize the risk of increased food allergy: A review

The first genetically modified (GM) crops approved for food use ( tomato and soybean) were evaluated for safety by the United States Food and Drug Administration prior to commercial production. Among other factors, those products and all additional GM crops that have been grown commercially have been evaluated for potential increases in allergenic properties using methods that are consistent with the current understanding of food allergens and knowledge regarding the prediction of allergenic activity. Although there have been refinements, the key aspects of the evaluation have not changed. The allergenic properties of the gene donor and the host ( recipient) organisms are considered in determining the appropriate testing strategy. The amino acid sequence of the encoded protein is compared to all known allergens to determine whether the protein is a known allergen or is sufficiently similar to any known allergen to indicate an increased probability of allergic cross-reactivity. Stability of the protein in the presence of acid with the stomach protease pepsin is tested as a risk factor for food allergenicity. In vitro or in vivo human IgE binding are tested when appropriate, if the gene donor is an allergen or the sequence of the protein is similar to an allergen. Serum donors and skin test subjects are selected based on their proven allergic responses to the gene donor or to material containing the allergen that was matched in sequence. While some scientists and regulators have suggested using animal models, performing broadly targeted serum IgE testing or extensive pre- or post-market clinical tests, current evidence does not support these tests as being predictive or practical. Based on the evidence to date, the current assessment process has worked well to prevent the unintended introduction of allergens in commercial GM crops. Copyright (C) 2005 S. Karger AG, Base

A novel approach for the detection of potentially hazardous pepsin stable hazelnut proteins as contaminants in chocolate-based food

Contamination of food products with pepsin resistant allergens is generally believed to be a serious threat to patients with severe food allergy. A sandwich type enzyme-linked immunosorbent assay (ELISA) was developed to measure pepsin resistant hazelnut protein in food products. Capturing and detecting rabbit antibodies were raised against pepsin-digested hazelnut and untreated hazelnut protein, respectively. The assay showed a detection limit of 0.7 ng/mL hazelnut protein or <1 mug hazelnut in 1 g food matrix and a maximum of 0.034% cross-reactivity (peanut). Chocolate samples spiked with 0.5-100 mug hazelnut/g chocolate showed a mean recovery of 97.3%. In 9/12 food products labeled "may contain nuts", hazelnut was detected between 1.2 and 417 mug hazelnut/g food. It can be concluded that the application of antibodies directed to pepsin-digested food extracts in ELISA can facilitate specific detection of stable proteins that have the highest potential of inducing severe food anaphylaxi