Cat, dog, and horse allergies: emerging new insights

Animal allergens, particularly those from cats, dogs, and horses, are significant risk factors for the development of allergic diseases in childhood. Managing animal allergies requires allergen avoidance and, when this is not feasible, specific immunotherapy. Patient history remains the cornerstone of diagnosis, providing the foundation for diagnostic algorithms. Extract-based tests, such as skin prick tests and specific IgE measurements, are essential for confirmation and screening. However, traditional extract-based diagnostic methods have notable limitations, as they are unable to distinguish between primary sensitization and immunological cross-sensitization, and also has the potential for both false negatives and false positives. Polysensitization may arise from either multiple independent sensitizations (co-sensitization) or cross-sensitizations, between homologous allergens. Due to complex cross-reactivity and polysensitization in mammals, extract-based tests are often insufficient in determining the true allergen, so molecular allergen testing should be used. Even with molecular testing, there is no consensus on how to define complex and intriguing sensitization patterns in mammals. In this report, we review the literature on cat, dog, and horse allergies and propose a novel approach to identifying complex sensitization patterns based on the current state of knowledge. We recommend that the evaluation of cat, dog, and horse allergies should begin with investigating genuine sensitization to Fel d 1, Can f 4/5, and Equ c 4, respectively. As a subsequent step, we propose a practical approach to determine primary allergen sensitization within the lipocalin group. Secondary sensitizations should then be evaluated in the context of recent contact history and presenting symptoms. While serum albumin is less strongly associated with true animal allergies, we suggest that it may serve as a complementary marker when considered alongside cross-reactive food allergen molecules.