Human Allergy to Cats and Dogs: Molecular and Environmental Determinants, Diagnosis, and Precision Management

Cat- and dog-derived allergenic proteins are important indoor exposure sources, but allergen exposure, IgE sensitization, and clinically manifest allergy are distinct biological and clinical states. Major molecules include the cat secretoglobin Fel d 1 and several dog lipocalins, including Can f 1, together with serum albumins, kallikreins, and other components that can contribute to species-specific sensitization or cross-reactivity. These proteins are transported in the environment on heterogeneous carriers such as dander fragments, dust, and aerosol particles, allowing both direct and indirect exposure. Clinical relevance depends on the concordance among exposure, molecular sensitization, symptoms, and host factors rather than on environmental detection alone. This narrative review integrates molecular allergen biology with environmental dissemination, IgE-mediated immune mechanisms, clinical phenotypes, diagnostic interpretation, and management. Particular emphasis is placed on the distinction between molecular homology, IgE cross-reactivity, and clinically relevant cross-allergy; on the complementary role and limitations of component-resolved diagnosis; and on the variable evidence supporting environmental control and cat- versus dog-allergen immunotherapy. Standard pharmacotherapy remains central to symptom control, whereas biologics and allergen-neutralizing approaches are restricted to specific indications or remain investigational. A precision-management framework therefore requires molecular results to be interpreted in the context of exposure-response concordance, clinical phenotype, and inflammatory disease characteristics.