BACKgrOUND: Atropine is a widely used anticholinergic drug. Its topical use is mainly restricted to ophthalmologic preparations, chiefly as mydriatic eye drops. Usually well tolerated, eye dryness, blurred vision and increased intraocular tension are the main adverse effects; allergic reactions are uncommon.CASE REPORT: A 71-year-old woman had a left corneous sore. Ten days after beginning treatment with atropine eye drops, she presented with conjunctival erythema and pruritus and ipsilateral facial aedema.RESULTS: Patch test with benzalconio-clorure (0.1% pet), thiomersal (0.1% pet), etilendiamine (1% pet), parabens (16% pet), phenylephrine (10% DMSO), cyclopentolate (Colicursi Cicloplejico®), tropicamide (Colicursi Tropicamida®) and with the chemically related mydriatic, hyoscine (Buscapina Boehringer Ing® 20 mg/ml), were negative. Patch test with atropine drops (Colircusi 0.5%®) and parenteral atropine (Braun Medical® 1 mg/ml) turned positive in 48 hours. Single blind challenge test with ocular cyclopentolate, phenylephrine, tropicamide and oral hyoscine were negative.CONCLUSIONS: We present a case of allergic conjunctivitis and facial aedeme caused by atropine. The positive patch test revealed a delayed hypersensitivity mechanism. Cross reactivity was absent between atropine and hyoscine. BACKgrOUND: Atropine is a widely used anticholinergic drug. Its topical use is mainly restricted to ophthalmologic preparations, chiefly as mydriatic eye drops. Usually well tolerated, eye dryness, blurred vision and increased intraocular tension are the main adverse effects; allergic reactions are uncommon. CASE REPORT: A 71-year-old woman had a left corneous sore. Ten days after beginning treatment with atropine eye drops, she presented with conjunctival erythema and pruritus and ipsilateral facial aedema. RESULTS: Patch test with benzalconio-clorure (0.1% pet), thiomersal (0.1% pet), etilendiamine (1% pet), parabens (16% pet), phenylephrine (10% DMSO), cyclopentolate (Colicursi Cicloplejico®), tropicamide (Colicursi Tropicamida®) and with the chemically related mydriatic, hyoscine (Buscapina Boehringer Ing® 20 mg/ml), were negative. Patch test with atropine drops (Colircusi 0.5%®) and parenteral atropine (Braun Medical® 1 mg/ml) turned positive in 48 hours. Single blind challenge test with ocular cyclopentolate, phenylephrine, tropicamide and oral hyoscine were negative. CONCLUSIONS: We present a case of allergic conjunctivitis and facial aedeme caused by atropine. The positive patch test revealed a delayed hypersensitivity mechanism. Cross reactivity was absent between atropine and hyoscine.