Allergic contact blepheroconjunctivitis with phenylephrine eyedrops –the relevance of late readings of intradermal tests

Allergic reactions to midriatic eyedrops are rare despite extensively used by ophthalmologists. Phenylephrine is responsible for 54-95% of cases reported in literature. We present the case of a 56-year-old man with blepharoconjunctivitis after instillation of phenylephrine 5%, tropicamide 0.5%, oxibuprocaine eyedrops. The patient reported good tolerance to the mentioned drugs. Immediate readings of prick and intradermal tests, performed with the suspected drugs, were negative. Late readings (48 and 72 hours) of epicutaneous tests were also negative. At 72 hours, prick and intradermal tests to phenylephrine were positive. Allergic blepharoconjunctivitis to phenylephrine was diagnosed. Phenylephrine is an extensively used midriatic that can act as a potent sensitizing agent and can be the cause of allergic contact reactions in exposed patients. With this case we illustrate the relevance of late readings of intradermal tests in the diagnosis of late hypersensitivity drug reactions. The authors discuss about possible mechanisms responsible for negative results of epicutaneous tests.