Quantification of the specific IgE antibodies to egg white is useful in the diagnosis of egg allergy. In children under 2 years of age with a background of immediate hypersensitivity after egg ingestion and presence of specific IgE antibodies to egg white of > or = 0.35 KU(A)/L, diagnostic challenge test is not necessary to establish the diagnosis of allergy to this food.

We evaluated the prevalence and characteristics of the principal foods implicated in 355 children diagnosed with IgE-mediated food allergy. Diagnosis was established on the basis of positive clinical history for the offending food, positive specific IgE by skin prick test and RAST, and open food challenge. Our results showed the principal foods involved in allergic reactions are: eggs, fish, and cow's milk. These are followed in frequency by fruits (peaches, hazelnuts and walnuts), legumes (lentils, peanuts and chick peas) and other vegetables (mainly sunflower seeds). The legumes demonstrated the highest degree of clinical cross-reactivity. Most patients with food allergy reacted to one or two foods (86.7%). Only 13.3% of patients reacted to 3 or more foods, mostly to legumes and fruits. We found that food allergy begins most frequently in the first (48.8%) and second (20.4%) years of life. Allergy to proteins of cow's milk, egg, and fish begins predominantly before the second year, demonstrating a clear relationship with the introduction of these foods into the child's diet. Allergy to foods of vegetable origin (fruits, legumes and other vegetables) begins predominantly after the second year.

Fish and its derived products play an important role in human nutrition, but they may also be a potent food allergen. Fish can be an ingested, contact, and inhalant allergen. Gad c I, a Parvalbumin, the major allergen in codfish, is considered as fish and amphibian pan-allergen. Prevalence of fish allergy appears to depend on the amount of fish eaten in the local diet. In Europe, the highest consumption occurs in Scandinavian countries, Spain and Portugal. In Spain, fish is the third most frequent allergen in children under 2 yr of age after egg and cow's milk. An adverse reaction to fish may be of non-allergic origin, due to food contamination or newly formed toxic products, but the most frequent type of adverse reactions to fish are immunologic-mediated reactions (allergic reactions). Such allergic reactions may be both IgE-mediated and non-IgE-mediated. Most cases are IgE-mediated, due to ingestion or contact with fish or as a result of inhalation of cooking vapors. Some children develop non-IgE-mediated type allergies such as food protein induced enterocolitis syndrome. The clinical symptoms related to IgE-mediated fish allergy are most frequently acute urticaria and angioedema as well as mild oral symptoms, worsening of atopic dermatitis, respiratory symptoms such as rhinitis or asthma, and gastrointestinal symptoms such as nausea and vomiting. Anaphylaxis may also occur. Among all the species studied, those from the Tunidae and Xiphiidae families appear to be the least allergenic.

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