D3.297 - De-labelling peanut allergy in a 19-year-old woman with detectable Ara h 2 sensitization: a real-life, exercise-augmented oral food challenge

Background

Ara h 2–specific IgE is considered a key biomarker for clinically relevant peanut allergy. Although levels >0.35 kU/L increase the likelihood of a positive oral food challenge (OFC), they do not reliably predict clinical reactivity or severity. Exercise is a recognized co-factor that may reduce reaction thresholds under real-life conditions. Accurate diagnosis is essential to prevent unnecessary dietary restriction and anxiety.

Case

A 19-year-old woman was referred for re-evaluation and potential de-labelling of suspected peanut allergy. At 3 years of age she experienced oral itching shortly after ingestion of food containing peanut sauce and vomiting approximately one hour later without cutaneous, circulatory or respiratory symptoms. She was evaluated in the emergency department, no allergy testing was performed and she was advised to avoid peanuts, however no acute medications, such as adrenalin auto-injector, were prescribed. Peanuts were initially avoided, although she tolerated trace exposures.

During re-evaluation, laboratory testing demonstrated sensitization to peanut-specific IgE 3 kU/L and Ara h 2–specific IgE 0.78 kU/L. Total IgE was 290 kU/L, birch-specific IgE was 89 kU/L and timothy-specific IgE was78 kU/L. Spirometry was normal with 2% reversibility and FeNO 17 ppb; no history of asthma was reported.

Subsequently, despite previous recommendations to avoid peanuts, she reported consuming peanut-containing bars, including roasted and raw peanuts, on multiple occasions without symptoms, suggesting possible real-life tolerance despite laboratory sensitization.

To replicate real-world exposure conditions, a supervised open OFC with raw peanuts was performed in late summer, using incremental doses (0.5 g, 2 g,5 g; cumulative 7.5 g) followed by standardized high-intensity physical exercise for 7 minutes. The patient remained asymptomatic during and after exertion, with stable vital parameters throughout observation.

Conclusion:

Low-level Ara h 2 sensitization does not necessarily indicate clinically relevant peanut allergy. Incorporating real-life elements, including exercise augmentation, into supervised OFC may improve diagnostic accuracy and support safe de-labelling in selected patients with persistent but clinically uncertain peanut sensitization.