Introduction: Allergic conjunctivitis is treated with oral anti-allergy agents or topical eye drops, but the response is often incomplete, and symptoms persist. We considered that topical treatment with an antihistamine ointment (diphenhydramine-Restamin Cream®) on the eyelids could be effective as supplemental therapy. This study investigates the efficacy and safety of Restamin Cream® for allergic conjunctivitis. Methods: In patients with allergic conjunctivitis, Restamin Cream® was applied to both eyelids twice a day for 2 weeks. There was a 2-week observation period before treatment and a 2-week washout period after treatment. Patients recorded symptoms (eye itching and watering) on a visual analogue scale for the entire 6-week period. Assessment of quality of life, evaluation of conjunctivitis, and measurement of visual acuity and intraocular pressure were conducted at the start of observation, at initiation of treatment, at completion of treatment, and at the end of washout. Results: 7 patients were enrolled; 5 completed the study and 2 discontinued due to adverse reactions. The quality of life score and objective ocular findings improved in all 5 patients. Visual analogue scale scores for itching and watering also improved significantly in 3 and 2 patients, respectively. Adverse reactions included local skin irritation in 3/7 patients, and transient blurred vision and eye pain in 1 patient each. There were no changes of visual acuity or intraocular pressure. Conclusions: Application of diphenhydramine ointment to the eyelids was effective for allergic conjunctivitis.