D3.283 - Oat-Induced Anaphylaxis: Allergenic Characterization in a Clinical Case

Oat allergy is an uncommon food allergy. While oats share structural homology with other cereal proteins, their allergenic repertoire is distinct, and clinically relevant sensitization may involve other allergens not yet identified.

A 54-year-old woman with no significant past medical history presented to the Allergy Department after developing rhinorrhea, conjunctival hyperemia, ocular and cutaneous pruritus, sneezing fits, a sensation of lingual edema, and patchy erythema, accompanied by vomiting and diarrhea, immediately after consuming oat milk. She required medical attention at her health center. Since then, she has avoided oats but tolerates other cereals. One year before, after eating almond nougat, she developed generalized pruritic wheal lesions. She now avoids all nuts.

Protein extracts were made from oat flakes, oat flour, oat bran, and pine nuts in order to study their protein and allergenic profiles by SDS-PAGE and IgE-Western blot, respectively.

Skin prick tests were positive for oats and pine nuts and negative for the rest of cereals and tree nuts. The prick by prick was for oat milk (4x3 mm) and pine nuts (5x4 mm), but negative for rolled oats and almonds. Total IgE 49.80 kU/L, and specific IgE to other cereals and tree nuts was negative.

Western blot demonstrated IgE binding to several proteins in oat bran, including a ~25 kDa band consistent with a 12S oat globulin previously described around 22.5 kDa. Also a ~50 kDa band is visible under non-reducing conditions and faintly detectable in reducing conditions in both bran and flour extracts, compatible with an oat serpin. Futhermore, we can see a ~37 kDa band present only under reducing conditions. No IgE-binding was observed in pine nuts.

Tolerance to pine nuts was confirmed.

We report a case of anaphylaxis induced by oats, a cereal with low allergenic potential, showing sensitization to multiple allergenic proteins without evidence of cross-reactivity with other cereals.