Mould spores and pollen are by no means the only triggers of rhinitis. House dust mites, pet allergens and all the other airborne allergens can be responsible, particularly for perennial rhinitis because they are in the environment all year round. Any foods can trigger rhinitis, just as they can asthma. Some foods may also cause cross-reactions in which people who are allergic to a particular plant's pollen may react to foods made from related plants. For instance, someone allergic to mugwort pollen may also react to camomile tea, made from a plant in the same family.
Inflammation causes itchiness and excessive mucus production.