Purpose: To evaluate the safety and efficacy of cromolyn sodium ophthalmic solution without preservative (Allergo- COMOD) compared with cromolyn sodium ophthalmic solution with preservative (Allergocrom) for the treatment of allergic conjunctivitis. Patients and Methods: Forty-seven patients with allergic conjunctivitis were randomly assigned to one of two treatment groups: Allergo-COMOD or Allergocrom four times daily. Data were collected at screening, baseline, and after one week and two weeks of therapy. Changes in main eye symptom score (MESS), the object change of signs determined by investigators, in particular regarding ocular itching or conjunctival redness, and any adverse events were analyzed. Results: The symptoms of subjects in both treatment groups achieved almost maximum improvement after one week of treatment, and remained stable during the treatment period. There was no difference in MESS reduction between the Allergo-COMOD and Allergocrom groups. No differences were noted between the two groups by the clinical investigators’ evaluations. There were also no significant adverse events throughout the study period. Conclusions: An Allergo-COMOD eye drop four times per day used in this study demonstrated satisfactory safety and efficacy features in the treatment of allergic conjunctivitis, when Allergocrom was used in the control group.