Cause
Allergic
rhinitis, often called hay fever, occurs when your
immune system overreacts to particles in the air that
you breathe—you are allergic to them. Your immune system attacks the particles
in your body, causing symptoms such as sneezing and a runny nose. The particles
are called
allergens, which simply means they can cause an
allergic reaction.
See a picture of how
an allergen affects the body
.
Several
types of allergens cause allergic rhinitis, including
pollens, mold,
dust mites,
animal dander, and cockroaches. Although polluted air
is not an allergen, it can irritate your nose and lungs. An irritated nose or
lungs may make an allergic reaction more likely when you breathe in an
allergen.