Abstract
Sleep terrors are a type of sleep disorder that is classified as parasomnias and is more common in children than in adults. Cetirizine is a histamine H1 antagonist that is US Food and Drug Administration approved for the treatment of allergic rhinitis and urticaria and has common adverse effects of drowsiness and headaches. We present a case of an adult man with a history of chronic sleep terror disorder and allergic rhinitis who developed worsening of his sleep terrors after initiation of cetirizine that subsequently resolved after discontinuing cetirizine and starting paroxetine.