BACKGROUND: Olanedine solution is a new antiseptic, and several cases of allergic contact dermatitis caused by the agent were reported in 2018; however, these cases were diagnosed based on positive results in 2-day closed patch testing of Olanedine solution "as is." OBJECTIVES: To present another case of Olanedine-induced allergic contact dermatitis and to analyze the optimal patch-testing method for this condition. METHODS: A 34-year-old Japanese female patient and 25 healthy control subjects were patch tested using wet filter paper, which had been treated with 15 μL Olanedine solution, and dried filter paper, which had been treated with 15 μL Olanedine solution and then dried. RESULTS: The patient and all of the control subjects exhibited false-positive reactions due to irritation in the 2-day closed patch tests with wet filter paper containing Olanedine solution "as is." The tests with dried filter paper produced a positive reaction on day 7 in the patient, and negative reactions in all control subjects. CONCLUSIONS: It is preferable to perform 2-day closed patch tests using filter paper with the test solution "as is," which had been dried before application in order to correctly diagnose antiseptic-induced allergic contact dermatitis.