prevalence rates ranging from a few percent of the allergic population to single cases (Hefle et al., 1996). Each of the eight major food allergens contains multiple allergenic proteins, many of which have not been fully characterized (Gendel, 1998).
2. Food Ingredients Some food ingredients such as edible oils, hydrolyzed proteins, lecithin, gelatin, starch, lactose, flavors, and incidental additives (e.g., processing aids), may be derived from major food allergens (Taylor and Hefle, 2001). The role that these ingredients play in food allergy has not been fully characterized. For example, lecithin is a common food ingredient which is often derived from soybeans. It is possible that soy lecithin, which contains residual protein, could elicit an allergic reaction in sensitive individuals (Muller et al., 1998; Gu et al., 2001). Another example is protein hydrolysate, which is often made from major food allergens such as soybeans, wheat, peanuts, or milk protein. Partially hydrolyzed protein ingredients can elicit allergic reaction. For example, hot dogs formulated with partially hydrolyzed casein have elicited allergic reactions in children allergic to cow’s milk (Gern, et al., 1991; Kocabas and Sekerel, 2003). Allergic reactions to partially hydrolyzed protein ingredients are more common than are reactions to extensively hydrolyzed protein ingredients (Bock and Atkins, 1989; Ellis et al., 1991; Saylor and Bahna, 1991; Kelso and Sampson, 1993; Niggemann et al., 1999).
Gelatins are ingredients derived from animals (e.g., cows, pigs) but also from the skin of various species of fish. A study of 10 fish allergic patients and 15 atopic individuals with eczema revealed that 3 and 5 individuals respectively had specific IgE to fish gelatin, suggesting the presence of allergenic protein (Sakaguchi et al., 2000). However, in a recent double-blind placebo-controlled food challenge (DBPCFC) study, all 30 fish allergic subjects in the study showed no response to a cumulative dose of 3.61 g of fish gelatin (Hansen et al., 2004).
Edible oils can be derived from major food allergens such as soybeans and peanuts, and they may contain variable levels of protein (Taylor and Hefle, 2001). The consumption of highly refined oils derived from major food allergens by allergic individuals does not appear to be associated with allergic reactions. For example, Taylor et al. (1981) and Bush et al. (1985) did not observe any reactions to refined peanut or soy oils in 10 and 7 allergic patients, respectively. On the other hand, unrefined or cold-pressed oils that contain higher levels of protein residues (Taylor and Hefle, 2001) may cause allergic reactions. For example, Hourihane et al. (1997b) reported that 6 of 60 peanut allergic individuals reacted to crude peanut oil but none responded to refined peanut oil. Similarly, Kull et al. (1999) reported that 15 of 41 peanut allergic children responded positively to crude peanut oil in skin prick tests, but none responded to refined peanut oil. The actual protein levels reported in various edible oils varies, probably due to differences in the oil, refining process, and the protein detection analytical method used. Crevel et al. (2000) reported that crude peanut and sunflower oils contained 100 to 300 µg/ml of protein, but that the most highly refined oils contained 0.2 to 2.2 µg/ml of protein. Intermediate protein concentrations were seen for partially processed oils. Teuber et al. (1997) showed that the amount of protein in both crude and refined gourmet nut oils varied both by type of oil and degree of processing; the reported values ranged
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