Orange allergy is estimated to account for up to 3–4% of food allergies. Major allergens identified in orange (Citrus sinensis) include Cit s 1 (germin-like protein) and Cit s 2 (profilin), while Cit s 3 (non-specific lipid transfer protein, nsLTP) and Cit s 7 (gibberellin-regulated protein) have also been described. The objective of this study was to investigate the presence and IgE-binding capacity of germin-like proteins in citrus fruits other than oranges. We describe five patients with immediate allergic reactions after orange ingestion. All patients underwent skin prick tests (SPT) to aeroallergens and common food allergens, prick-by-prick testing with orange, lemon, and mandarin (pulp, peel, seeds), total IgE, specific IgE (sIgE), anaphylaxis scoring (oFASS), and the Food Allergy Quality of Life Questionnaire (FAQLQ-AF). Protein extracts from peel and pulp of orange, lemon, and mandarin were analyzed by Bradford assay, SDS-PAGE, and IgE immunoblotting using patient sera. Selected bands were identified by peptide mass fingerprinting. A 23 kDa band was recognized by all five patients in orange (pulp and peel), lemon (peel), and mandarin (peel). This band was consistent with Cit s 1, a germin-like protein already annotated in the IUIS allergen database for orange but not for lemon or mandarin. Peptide fingerprinting confirmed the germin-like identity of the 23 kDa bands in all three citrus species. Germin-like proteins of approximately 23 kDa were identified as IgE-binding components in peel extracts of orange, lemon, and mandarin, and in orange pulp. These findings suggest a potential shared allergen across citrus species that may contribute to allergic reactions independent of LTP sensitization.

Orange allergy is estimated to account for 3% of food allergies. Cit s 1 (germin-like protein) and Cit s 2 (profilin) have been identified as major allergens. Also, Cyt s 3 (lipid transfer protein) and Cyt s 7 (gibberellin-regulated protein) have been described as orange allergens. This study focuses on the unusual occurrence of orange allergy in five patients. Materials and methods: We report five cases of patients with immediate allergic manifestations after ingestion of orange. Skin prick-tests to common aeroallergens, and different foods. Prick by prick with orange, lemon pulp mandarin (peel, pulp and seeds). Anaphylaxis score; Total IgE, Serum-specific IgE and food allergy quality of life questionnaire. Allergenic extracts were prepared from orange (Citrus sinensis), lemon (Citrus lemon) and mandarin (Citrus reticulata) peel and pulp. Protein characterization was determined by Bradford and SDS-PAGE and sera by immunoblot. Selected proteins were identified by peptide fingerprinting. Results: A 23 kD band was recognized by all 5 patients in orange (pulp and peel), lemon (peel) and mandarin (pulp and peel), having already been annotated in IUIS in the case of orange as germin (Cit s 1). To send the 23 kDa bands for peptide fingerprinting, SDS-PAGE of the 3 fruits was performed and as a positive control we used the 23 kDa band from orange. Together, the 23 kDa bands from orange, lemon and mandarin peel were cut out and sent for peptide fingerprint analysis, yielding the germin like protein sequence in all cases. Conclusions: A band of 23 kDa (germin-like protein) appears common in orange (annotated in IUIS as germin), lemon and tange-rine peel. Not previously described in IUIS in lemon and mandarin and confirmed as germin. Germin was in the peel of the 3 fruits and in the orange pulp, but not in lemon or mandarin.