Cetirizine-induced psychosis in a young adult with erythema multiforme.

We describe a case of a young man, taking no other routine medications, presenting with erythema multiforme and cetirizine-induced psychosis with re-challenge evidence. On retrospective elicitation of history, it was found that he had been involved in a motor vehicle collision 4 months prior and was a daily cannabis user; there were no objective abnormalities by MRI and neurological evaluations. Although rare, cetirizine-induced psychosis is an important adverse drug reaction that warrants the attention of healthcare practitioners.