A 12-year-old girl was referred to our hospital owing to repeated anaphylactic reactions induced by exercise after meals. Food-dependent exercise-induced anaphylaxis (FDEIAn) was suspected. However, sequential tests of typical foods, including egg, milk, soy, and wheat, in combination with exercise, were all negative.
The results of the skin prick test (SPT) for Citrus unshiu and specific IgE test for orange and grapefruit were positive. Although no symptoms were noted after an exercise challenge combined with the ingestion of only Citrus unshiu, an anaphylactic reaction was induced by additional acetyl-salicylic acid. From these results, she was diagnosed with FDEIAn due to the ingestion of Citrus unshiu. Because the SPT results for other citrus fruits (including orange, grapefruit, lemon, yuzu, sudachi, ponkan, and iyokan) were all positive, it was suggested that these fruits demonstrate cross-reactivity with each other. Since the girl eliminated citrus fruits from her diet, she has not developed any anaphylactic symptoms. Citrus fruits are not known to cause FDEIAn, but the findings of this case suggest that it is necessary to recognize them as a causative allergen of FDEIAn.