Hay fever
is an immune disorder characterized by an allergic response to pollen
grains and other substances. Also known as allergic rhinitis, there are
two types: seasonal, which occurs only during the time of year in which
certain plants pollinate, and perennial, which occurs all year round. (A
related problem,
nonallergic rhinitis, shares symptoms with hay fever but isn't caused by the type of reaction that's typical with allergies.)
Typically, if you suffer from hay fever in the spring, you're
probably allergic to tree pollens. Grass and weed pollens may be causing
your allergic reaction during the summer. In autumn, weeds may plague
you, and fungus spores cause problems primarily from late March through
November but can be present year round.
People with year-round (perennial) hay fever are usually allergic to
one or more allergens found indoors. These include house dust mites,
feathers, and animal dander (the tiny skin flakes animals such as cats
and dogs shed along with fur), all of which may be found in pillows, and
bedding, heavy draperies, upholstery, and carpeting. Another common
allergen, mold, is usually found in damp areas such as bathrooms and
basements.
What Causes Hay Fever?
If you suffer from hay fever (allergic rhinitis), it's because
your immune system views harmless inhaled pollen or other allergens as
dangerous substances invading your body. Your system overreacts,
flooding your bloodstream with chemicals like histamine and
leukotrienes, which inflame the lining of your nasal passages, your
sinuses, and your eyelids and also set in motion other symptoms
associated with hay fever, such as sneezing.
All of these symptoms are meant to protect your body either by
trapping and expelling the allergen or by swelling body areas, such as
the nasal passages, so the allergen can't enter. As a result of
congestion in the veins in the lining of your sinuses, dark circles,
commonly known as allergic shiners, may appear under your eyes. If you
have perennial allergic rhinitis, they may be present all year round.
The swelling of your nasal membranes may also close the sinus drainage
openings, causing sinusitis. Rhinitis may also be associated with nasal
polyps -- small, non-cancerous growths; nosebleeds are also common
during hay fever attacks.
Hay fever is often an inherited trait (genetically determined).
The majority of patients with hay fever have a parent or sibling who
also has allergies. People with asthma or eczema (allergic dermatitis)
are more likely than others to develop hay fever; and about one-third of
those with allergic rhinitis also have at least mild, intermittent, allergic asthma.
What Is Hay Fever?
