from 10 to 60 µg/ml for various unrefined oils and from 3 to 6 µg/ml for the refined oils. Other investigators reported undetectable levels of proteins in refined edible oils (Hoffman et al., 1994; Yeung and Collins, 1996; Peeters et al., 2004) using assays with detection sensitivities of <0.3 ng/ml (Peeters et al., 2004) and 0.4 mg/kg (Yeung and Collins, 1996).
Starch, which is a widely used ingredient, is often derived from corn which is not a major food allergen. However, starch can also be derived from wheat, and may contain trace levels of wheat protein. For example, Lietze (1969) reported the presence of antibodies to wheat starch in several wheat sensitive individuals. However, the allergenicity of wheat starch for sensitive individuals has not been clinically evaluated (Taylor and Hefle, 2001).
A wide variety of flavoring substances are used in foods, but only a few are derived from known allergens (Taylor and Dormedy, 1998). As such, IgE-mediated allergic reactions to flavorings are rare, although a few cases have been documented involving hydrolyzed proteins. For example, several milk allergic individuals reacted to either hot dogs or bologna containing partially hydrolyzed casein as part of the natural flavoring used in the formulation of these products (Gern et al., 1991). Two other milk-allergic individuals reacted to milk protein in the natural flavoring used in a dill pickle-flavored potato chip (St. Vincent and Watson, 1994). The presence of peanut flour in the natural flavoring of a packaged soup elicited a reaction in a peanut-allergic individual (McKenna and Klontz,
Allergens, or proteins derived from allergenic foods, may be present in foods as the result of cross-contact during processing and handling. The term “cross-contact” describes the inadvertent introduction of an allergen into a product that would not intentionally contain that allergen as an ingredient. Cross-contact may occur when a residue or other trace amount of a food allergen is present on food contact surfaces, production machinery, or is air-borne, and unintentionally becomes incorporated into a product not intended to contain, and not labeled as containing, the allergen. Cross-contact may also result when multiple foods are produced in the same facility or on the same processing line, through the misuse of rework, as the result of ineffective cleaning, or may result from customary methods of growing and harvesting crops, as well as from the use of shared storage, transportation, or production equipment. Cross-contact of foods with allergens has been shown to lead to allergic reactions in consumers on numerous occasions (Gern et al., 1991; Jones et al., 1992; Yunginger et al., 1983). Much cross-contact can be avoided by controlling the production environment.
Design of Food Challenge Studies
A history of clinical reaction to a food and a positive skin prick test or the presence of food-specific IgE antibodies in serum are sufficient to establish that an individual has an allergy to that food. However, none of these reliably predicts the level of patient sensitivity to low doses of the food. At present, the level of individual sensitivity can
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