L
leukotrienes Molecules that instigate INFLAMMA-
TIONduring an IMMUNE RESPONSE. Mast cells secrete
leukotrienes in response to stimulation by
IMMUNOGLOBULINE (IgE). Leukotrienes are derived
from arachidonic acid, which is the same base
source (precursor) as that of PROSTAGLANDINS, the
other primary agents of inflammation. The actions
of leukotrienes are most apparent in ASTHMA, in
which they cause the bronchioles (tiny bronchi
deep within the LUNGS) to constrict. Leukotriene
release becomes more rapid with each HYPERSENSI-
TIVITY REACTION. Leukotrienes also attract
eosinophils, which cause swelling in the bronchial
mucosa (mucous membrane lining of the
bronchi). In inflammatory responses outside the
pulmonary system, leukotrienes attract neu-
trophils with similar effect (swelling and discom-
fort). Eosinophils and neutrophils are types of
granulocytes.
See also GRANULOCYTE; HISTAMINE; MAST CELL.
living with allergies About 50 million Ameri-
cans live with allergies—to pollens, animal dan-
ders, latex, fragrances, foods, drugs, and other
substances—that cause them to alter their
lifestyles. Most people can reduce exposure to
allergens enough to lessen symptoms.
Outdoor Allergens
The primary outdoor allergens are pollens and
molds. Pollen is the powdery and often micro-
scopic granules that are the male cells of plants.
The plant disperses pollen into the air, which car-
ries it to other plants. The dusting of pollen on
plants of the same species fertilizes them, permit-
ting them to propagate. The pollens most likely to
cause a HYPERSENSITIVITY REACTIONare grasses and
trees. Tree pollens are highest in early spring and
grass pollens (including weeds) are highest in
early summer. Both tree and grass pollens remain
high through summer and into early autumn in
most regions of the United States. Molds are also
microscopic, airborne substances, though correlate
to weather conditions rather than seasons. Molds
are highest when the weather is cool and wet.
Raking leaves in the autumn is a major risk for
exposure to molds.
Many weather reports include local pollen
counts and mold counts. Counts that are moder-
ate to high are likely to cause ALLERGYsymptoms
in people who are allergic; very high counts may
cause symptoms in people who do not typically
have seasonal allergies. Because pollens and molds
are airborne, it is difficult to escape them. Aller-
gists recommend ANTIHISTAMINE MEDICATIONS or
DESENSITIZATION to mitigate symptoms. Staying
indoors is not usually an effective or practical
strategy.
Steps that may help include taking off outdoor
clothing immediately upon coming indoors and
washing the face, arms, hands, and other exposed
areas with soap and water (showering is best).
Washing the hands especially helps limit spreading
pollen to the NOSEand EYEvia contact. Some peo-
ple can reduce their symptoms by wearing a mask
over the face and nose during outdoor activities
when pollen and mold counts are high. As well,
pollen counts are highest in the early morning.
Central air-conditioning in the home and in the
car helps filter pollens and other particulates.
Being outdoors brings the risk of exposure to
other allergens as well. People who are allergic to
the sting of bees and wasps have a high risk of
exposure during spring and summer when plants
are in bloom. Wasps and related stinging insects
become active in the autumn, especially in279