Allergic rhinitis is the inflammation of nasal passage, usually associated with watery nasal discharge and itching of nose and eyes. Rhinitis which occurs during a specific season is called "seasonal allergic rhinitis ". When it occurs throughout the year, it is called " perennial allergic rhinitis .
Although childhood hay fever tends to be more common, allergic rhinitis can occur at any age and usually occurs after years of repeated inhalation of allergic substance.
It usually occurs when a body is exposed to certain allergens such pollens, dust, animal dander (particles of shed skin and hair) and food products.
When caused by pollen of any plant, it is called pollinosis, and, if specifically caused by grass pollen, it is known as hay fever.
In such individuals, the allergen triggers production of the antibody immunoglobulin E (IgE), that in turn stimulates secretion of the “allergy chemical” histamine.