• Bla g 2 allergen;
  • cockroaches;
  • contamination;
  • flour

In some situations, organ-based classification of allergic diseases is not appropriate (1). Mites and insects cause inhalant IgE-mediated asthma and/or rhinoconjunctivitis. However allergic symptoms, including anaphylaxis, have been reported after ingestion of insects (2) and baked goods made from flour contaminated with mites (3).

Different allergens including storage mites (4), flour beetles and moths cause occupational asthma in bakers (5) and workers exposed to grains (6,7). This study reports the presence of Bla g 2 allergen, derived from German cockroach, in flour samples.

We obtained 120 different flour packages from 19 brands, including four popular brands, from four Tampa supermarkets. These packages were wheat 48/120 (39%), wheat-processed mixes 27/120 (23%), cornmeal 38/120 (32%), and others 7/120 (6%).

Samples from all packages were heated at 350°F for 30 min. Fresh and heated samples were extracted, and Bla g 2 allergen levels of fresh and heated and Der p 1 and Der f 1 of fresh samples measured by ELISA. Mite counts were performed in all fresh samples. The following comparisons (Wilcoxon test) of Bla g 2 levels were performed: 1) fresh vs heated; 2) among supermarkets; 3) among types of flour; and 4) among the four most popular brands.

Bla g 2 was present in all (100%) fresh and 90/120 (75%) heated samples, and its values were 1.272 ± 0.776 and 0.886 ± 0.990 (P < 0.0001), respectively. Twenty-three of 120 (19.2%) fresh and 7/120 (5.8%) heated samples have Bla g 2 levels ≥ 2 U/g (considered the sensitization threshold).

There were no significant differences among Bla g 2 levels found in flour from the four different supermarkets but there were differences among brands (Fig. 1), which suggests that cockroach contamination most likely does not occur at the supermarket but at the factory or mill. Bla g 2 levels in wheat, wheat mixes, and cornmeal are 1.784 ± 0.382, 2.067 ± 0.302, and 0.485 ± 0.054 U Bla g 2/g, respectively, P < 0.001 wheat and wheat mixes vs cornmeal. Mites were absent in all samples and Der p 1 and Der f 1 levels below the detection level of the techniques, which supports the observation that mite contamination most likely occurs at home after the package is opened (3).


Figure 1.  Bla g 2 determination in flour samples from the four commonest brands.

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Cockroach allergens can potentially sensitize and cause IgE-mediated asthma and/or rhinoconjunctivitis in individuals exposed to flour inhalation, such as bakers and millers, especially those with an atopic background, who become sensitized by extremely low doses of allergen (1).

With mites, IgE-mediated anaphylaxis has been associated with the ingestion of large amounts of allergen (more than 5000 mites/g of food). However, milder reactions may occur when lower amounts of allergen are ingested (3). Whether Bla g 2 ingestion can cause sensitization and IgE-mediated allergic manifestations is not known, but it should be suspected when the role of other etiologic agents is ruled out. In conclusion, cockroach allergens could be an allergen involved in occupational asthma and cause sensitization and allergic symptoms after ingestion of baked goods.


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  2. References
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    Freye HB, Esch RE, Litwin CM, Sorkin L. Anaphylaxis to the ingestion and inhalation of Tenebrio molitor (mealworm) or Zophobas morio (superworm). Allergy Asthma Proc 1996;17:215219.
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