Why might someone get itchy eyes when around cats?

Common allergy: Cats are a common source of allergens which elicit allergic symptoms in many sensitive people. In fact, “This protein is contained in skin cells, urine and saliva, and triggers an allergic reaction. Dander is dead skin cells that are regularly sloughed off and replaced by new skin cells. All cats produce dander, but not all people are allergic to it.” (Excerpted from PetMD).