Allergy is overreaction of the immune system. The overreaction of the body’s immune system to specific substances may not be necessarily harmful but may cause a lot of inconvenience.
Antihistamine drugs, such as Generic Allegra and Generic Clarinex used for treating allergies use its active ingredient to block histamine H1 receptor. Once this happens, the cells containing histamine receptor stop firing allergic chemicals which cause alleviation of the allergic problems. Some of the seasonal allergies which would be treated by Antihistamine drugs are runny or itchy nose, sneezing, itchy throat, and watery, itchy, or red eyes.