Allegra Get all-day relief from tough allergy symptoms with Allegra 24 hour tablets. Relieve your hay fever and allergy symptoms like runny nose sneezing itchy watery eyes itchy nose or itchy throat. Allegra starts working in one hour twice as fast as Claritin and won’t leave you feeling drowsy like zyrtec. That is why it’s the 1 allergist-recommended allergy brand.