FEATURE
IT’S JUST MY ALLERGIES…OH REALLY?! PART 1
History and Pathophysiology of Allergic Diseases
F. Tolis Simon, MD
N
asal upper airway symptoms affect
millions of Americans and pa-
tients are affected for many years.
The pathophysiology, differential
diagnosis and associated condi-
tions including the oral allergy syndrome
are all important to consider when treating
patients with “just allergies.”
BACKGROUND AND PATHOPHYSIOLOGY
Allergic rhinitis is characterized by nasal congestion, sneezing, nasal
pruritus, and rhinitis that is due to environmental allergen exposure
in susceptible individuals. It has a prevalence of 15 percent based
on physician diagnosis in the United States depending on age, and
this is thought to be increasing. (1) Exposure to both indoor and
outdoor allergens cause symptoms in the person with the appro-
priate genetic predisposition. A family history of allergy, asthma or
atopic dermatitis confers significant risks to an individual. Studies
have shown that if one parent is atopic, the risk may be 30 percent,
and if both parents are atopic, the risk can be estimated to be as
high as 50 percent. If neither parent is allergic, the risk decreases
to 20 percent. (1, 3)
The environment and allergen exposure are also important,
as described by the hygiene hypothesis. (1, 3) In this mechanism,
individuals develop an allergic t-helper subtype 2 (TH2) response
if one is exposed to a “sterile environment” in which bacteria are
not present, causing the immune system to mount less of a response
to infection and more of an allergic IgE response to environmental
allergens. Conversely, if an individual is in less of a “sterile environ-
ment” and is exposed to bacteria, such as endotoxin, the immune
system switches its focus to fighting infection and is stimulated
to make a t-helper subtype 1 (TH1) response to fight pathogens
to protect the individual and less TH2 allergen response is made.
Once the allergic TH2 response is established, IgE production
occurs and mast cells become covered with IgE on their surface
leading to sensitization. Upon re-exposure to allergen, crosslinking
of IgE occurs with subsequent immediate mast cell degranulation
of histamine, leukotrienes, cytokines and other mediators trigger-
ing further activation of the immune system characterized by late
phase cellular inflammation. (1) Atopy becomes the issue and can
be characterized by increased risk of atopic dermatitis, food allergy,
allergic rhinitis and asthma. Table I summarizes risk factors for the
development of allergic rhinitis. (1, 3)
TABLE I. RISK FACTORS FOR ALLERGIC RHINITIS
Increased Risk Decreased Risk
Family History of Allergy Increased Numbers of Siblings
Serum IgE >100 Iu/ml before
age 6 Grass Pollen Count
Higher Social Economic Class Farm Environment
Positive allergy prick skin test Mediterranean diet (High in
antioxidant and Omega 3 fatty
acids)
Maternal smoking Particulate air pollution
Co-morbidities associated with allergic rhinitis include allergic con-
junctivitis, eustachian tube dysfunction, chronic sinusitis, asthma,
obstructive sleep apnea, decreased quality of life, poor school and
work performance, and potentially other conditions. (1, 3)
ALLERGEN EXPOSURE AND AVOIDANCE
As things relate closer to home, the allergen exposure in Louisville
is important to recognize. Louisville consistently ranks in the top
five allergic cities to live in based on our high pollen counts and
our climate in the Ohio Valley with lush vegetation, particularly
Bluegrass. (4)
According to the Allergy and Asthma Foundation of America
(AAFA) in 2014, Louisville led the nation as the most difficult place
to live with springtime allergy. In 2018, Louisville rated second.
(4) The recognition of high pollen counts causing individuals to
suffer with allergic symptoms has been widely noted. Some helpful
measures to reduce pollen exposure are to keep windows and doors
closed and use air conditioning. Participation in outdoor activities
should be in the early morning or in the late evening when pollen
counts are lower. (3) Tree pollination typically starts in mid-Feb-
(continued on page 20)
JULY 2018
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