IGHE and hypersensitivity reaction disease: SAC and PAC are considered as the most prevalent allergic ocular conditions, affecting 15–20% of the population.[110] The pathogenesis is predominantly an IgE-mediated hypersensitivity reaction, and allergen-specific IgE antibodies are found in almost all cases of SAC and PAC.[111] Activation of mast cells contributes to increased levels of histamine, prostaglandins, and leukotrienes in the tear film.