Clarinase tablets to treat seasonal allergy symptoms. Clarinase helps relieve cold or flu symptoms, as well as sinus allergies such as sneezing, runny nose, watery eyes, and difficulty breathing. Clarinase tablets contain a group of anti-allergy medications with decongestants that reduce swelling of the nasal membranes and improve airflow, as well as others. One of the diseases caused by an increase in histamine.