Alcaftadine is primarily used as an antihistamine in ophthalmic solutions to treat allergic conjunctivitis. It works by inhibiting histamine receptors, reducing symptoms like itching, redness, and swelling in the eyes. This makes it effective for managing seasonal and perennial allergies that affect the eyes. It is often preferred due to its rapid onset of action and long-lasting relief, providing comfort for patients with eye-related allergic reactions. Additionally, its dual mechanism of action, which includes stabilizing mast cells, further enhances its efficacy in preventing and alleviating allergic symptoms.