Clinically proven 24 hour relief of indoor and outdoor allergies. All day and all night relief of sneezing, runny nose, itchy, watery eyes, and itchy nose or throat. Clinically proven relief in 60 minutes. Xyzal is as effective at hour 24 as hour 1. Xyzal Allergy 24 hour is designed to provide continuous, 24-hour, full prescription strength relief of your worst allergy symptoms.