Possible induction of food allergy during mite immunotherapy.
Sera of 17 patients receiving immunotherapy for house-dust mite allergy were tested for IgE antibodies against snail and shrimp. Serum samples were taken at the start of immunotherapy and 14-20 months later. While the average IgE response to mite, Der p 1, and Der p 2 did not alter significantly, the average response to snail showed a significant increase. This included two conversions from negative to strongly positive. These novel IgE antibodies against snail were shown to be cross-reactive with mite. Three patients had a positive RAST for shrimp. For one of them, a strong increase of IgE against shrimp (and snail) was observed. In 2/3 snail/shrimp-positive sera, IgE antibodies against the cross-reactive allergen tropomyosin from mite, snail, and shrimp were demonstrated. A clear IgE response to snail (> 10% binding in a snail RAST) was confirmed by a positive skin prick test (SPT) for 6/10 patients. The two patients with antitropomyosin IgE also had a positive SPT for shrimp, and demonstrated the oral allergy syndrome (OAS) after eating shrimp. The observations in this study indicate that house-dust mite immunotherapy is accompanied by the induction of IgE against foods, including tropomyosin-reactive IgE. Food allergy (OAS) was observed in patients that had IgE antibodies against this cross-reactive allergen. In conclusion, induction of IgE during mite immunotherapy might occasionally cause allergy to foods of invertebrate animal origin.