D3.296 - Alpha-gal Syndrome with Concomitant Milk Sensitization in a Patient with Asthma and Allergic Rhinitis: A Case Report

Introduction: Most IgE-mediated food reactions are directed against protein allergens; however, carbohydrate determinants can also elicit clinically significant symptoms. Alpha-gal (galactose-α-1,3-galactose) is a mammalian glycan epitope absent in humans and Old World primates, which may lead to IgE sensitization and hypersensitivity after exposure. In sensitized individuals, ingestion of mammalian meat can provoke urticaria or anaphylaxis, often with a delayed onset. Increasing evidence supports arthropod bites—particularly ticks—as a key trigger for initiating alpha-gal sensitization. Recognition is clinically important because symptoms may be intermittent and dietary triggers may extend beyond meat in selected patients.

Case: A 43-year-old woman with asthma and allergic rhinitis since childhood presented with a 3-month history of recurrent urticaria predominantly triggered after eating red meat. She also reported worsening urticaria with milk and dairy products. Physical examination was unremarkable, including normal respiratory and skin findings. Laboratory tests revealed total IgE 601 IU/mL, baseline serum tryptase 4.3 ng/mL, alpha-gal specific IgE 2.09 kU/L (reference <0.10), Dermatophagoides pteronyssinus specific IgE 0.42 kU/L, and milk specific IgE 0.65 kU/L. A non-specific bronchial provocation test with methacholine was positive (PC20 = 2.93 mg/mL). Controller therapy for asthma and allergic rhinitis was initiated, and avoidance of red meat and dairy products was recommended.

Discussion/Conclusion: Based on the compatible clinical history and positive alpha-gal specific IgE, alpha-gal–associated red meat allergy was considered. Cross-reactivity to milk carbohydrates has been reported in a subset of alpha-gal–sensitized patients; however, in this case, positive milk specific IgE supported concomitant milk allergy rather than isolated cross-reactivity. The coexistence of house dust mite sensitization, allergic rhinitis, and asthma highlights the importance of evaluating comorbid atopic conditions and tailoring avoidance and management strategies in patients with suspected alpha-gal syndrome.