Allergic conjunctivitis is a clinical reaction to environmental allergens and is manifested by ocular itching caused by IgE-induced mast cell degranulation. Bepotastine besilate is a selective H(1)-antagonist with mast cell stabilizing properties. This report examines the reduction of ocular itching integrated from two conjunctival allergen challenge (CAC) clinical trials comparing bepotastine besilate ophthalmic solution (BBOS) 1.5% to placebo in subjects with a history of allergic conjunctivitis. Two phase III, double-masked, placebo-controlled, parallel-group, CAC clinical trials evaluated BBOS 1.5% versus placebo to reduce ocular itching. Eligible subjects were randomly assigned 1:1 to either BBOS 1.5% (n = 78) or placebo (n = 79). Ocular itching was graded by subjects using a standardized scale (0–4 U). Adverse events and ophthalmic clinical findings were recorded for safety. BBOS 1.5% was superior to placebo for reducing CAC-induced ocular itching (p < 0.0001) as early as 3 minutes post-CAC and for at least 8 hours after dosing. Post hoc analyses examining several populations also showed a significant improvement (p < 0.0001) for subjects with more severe itching response at screening and for the proportion of subjects with complete or nearly complete resolution of CAC-induced itching, both outcomes supporting the clinical benefit of BBOS 1.5%. Adverse events were generally transient and mild. BBOS 1.5% is safe and effective in the treatment of ocular itching associated with allergic conjunctivitis within 3 minutes of a CAC and with a sustained duration of action of at least 8 hours. (ClinicalTrials.gov numbers: NCT00424398 and NCT00586664).