Ocular Allergy Within the Framework of the EAACI Nomenclature of Allergic Diseases and Hypersensitivity Reactions

Ocular allergy encompasses a heterogeneous group of diseases with overlapping clinical features and complex immunopathological mechanisms. This often creates challenges in classification and, consequently, in optimizing patient management. The nomenclature published in 2023 by the European Academy of Allergy and Clinical Immunology (EAACI) addresses these issues by redefining these conditions and linking clinical phenotypes and environmental modifiers to underlying types of hypersensitivity. This framework enhances diagnostic precision and supports mechanism-guided management. This article applies the EAACI approach based on hypersensitivity types to ocular allergy. The examples addressed include seasonal and perennial allergic conjunctivitis, driven mainly by type I and IV hypersensitivity reactions; vernal and atopic keratoconjunctivitis, involving mixed type I, IVb and IVa pathways; giant papillary conjunctivitis, a tissue-driven type V reaction; and contact blepharoconjunctivitis, a type IVa delayed hypersensitivity reaction with additional components. Distinct endotypes-such as local or acute allergic conjunctivitis, dupilumab-induced ocular disease, and vernal keratoconjunctivitis/atopic keratoconjunctivitis overlap-further illustrate heterogeneity, with the ocular surface microbiome emerging as a modifier. Diagnostics are increasingly aligning with mechanisms, and the EAACI framework translates this complexity into a mechanism-indexed map; this supports the selection of responders for targeted interventions while minimizing overtreatment.