Hay fever
Allergic rhinitis, also called pollinosis, hay fever or nasal allergies, and often also written together as hayfever, is a collection of symptoms, predominantly in the nose and eyes, that occur after exposure to airborne particles of dust, dander, or the pollens of certain seasonal plants in people who are allergic to these substances..

Hay fever, like all allergic reactions, is caused by allergens, foreign "invaders" that enter your body by inhalation, by swallowing, or through your skin.



• In hay fever, the allergens are airborne substances that enter your airways (mouth, nose, throat, and lungs) via your breathing and the linings of your eyes and sometimes ears via direct contact.


Most of the time it is difficult to identify a specific allergen.
• Once these allergens come in contact with your airway, the white blood cells of your immune system produce antibodies to the offending substance. This overreaction to a harmless substance is often called a hypersensitivity reaction.


The antibody, called immunoglobulin E, or IgE, is stored on special cells called mast cells.


When the antibody comes in contact with the corresponding antigen, they promote release of chemicals and hormones called "mediators." Histamine is an example of a mediator.


It is the effects of these mediators on organs and other cells that cause the symptoms of the allergic reaction, in this case hay fever.
The most common allergens in hay fever are pollens.


Pollen is small particles released by flowering plants.


It is moved around by wind to other plants of the same species, which it fertilizes so that the plant can bloom again.


Pollens from certain types of trees, grasses, and weeds (such as ragweed) are most likely to cause reactions. Pollens from other types of plants are less allergenic.


The time of year when a particular species of plant releases pollen, or "pollinates," depends on the local climate