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Food Allergies are increasing in frequency, now affecting
8% of young children and almost 5% of adults. Food Allergies, which
are immunologically adverse reactions to foods, must be distinguished
from Food Intolerances, which result from other factors such as lactose
deficiency.
While numerous foods can cause allergic reactions, a few classes of
foods are responsible for the vast majority of food allergies. In
young children, milk, eggs, and peanuts are responsible for most of
the food allergies, while peanut, tree nuts, fish, and shellfish account
for most of the food allergy in adults. In adults and older children,
most of the food allergies are lifelong, whereas in children less
than 5 years old, most will develop a tolerance to milk and eggs.
Some even develop tolerances to peanuts. Oral Allergy Syndrome is
an interesting subclass of Food Allergies in which patients develop
mild oral and perioral pruritis, tingling, and angioedema to certain
raw fruits and vegetables because the fruits and vegetables share
allergenic proteins with unrelated plant pollens. For instance, patients
with birch pollen allergy may develop oral symptoms to raw carrots,
apples, pears, and kiwi.
Allergic reactions to foods vary from mild discomfort to life-threatening
anaphylaxis. Oral Allergy Syndrome reactions are uncomfortable,
but rarely life-threatening. Some eczema patients will experience
flares when they eat raw fruits and vegetables associated with their
pollen allergies. Acute Urticaria is a common manifestation of food
allergy (Food Allergy is not usually associated with Chronic Urticaria),
and may be associated with respiratory compromise from oropharyngeal
swelling. Patients with a history a mild allergic reactions to foods
are at risk for severe reactions on re-exposure, including nausea,
vomiting, diarrhea, wheezing, and cardiovascular collapse; It is
essential that all patients with a history of systemic allergic
reactions to foods be counseled to avoid the foods completely and
to carry and know how use an Epipen.
Patients with peanut or tree nut allergy, even those with a history
of mild reactions, are the most common victims of fatal anaphylaxis
to foods. Most patients with fatal or near-fatal anaphylaxis also
have a history of asthma. Having and knowing how to use an Epipen
dramatically decreases the risk of a fatal anaphylactic reaction,
although is not foolproof; 10% of victims of fatal anaphylaxis do
receive Epinephrine in a timely manner.
As with most diseases, the medical history is the single most important
tool in the diagnosis of food allergy. Skin prick testing remains
the single most accurate method of diagnosing a food allergy, while
in vitro assays such as IgE RAST and ImmunoCAP play an important
role as well. Occasionally, physician monitored oral challenge is
required to confirm the diagnosis of a food allergy or to determine
whether a patient has become tolerant to the relevant food.
Oral Allergy Syndrome may respond to immunotherapy to the relevant
pollens, but for all other food allergies Avoidance in the mainstay
treatment. This is a drastic therapy for many patients, and it is
unfortunate that many are placed on overly restrictive diets based
on erroneous diagnoses. It is important to select the appropriate
tests and to apply them to the clinical history to ensure that the
diagnosis is accurate. Patients at risk for anaphylaxis should always
have an Epipen with them. Young children should be retested at intervals
to determine whether they have developed tolerance.
About The Author
Dr. Gary B. Moss received a BA in Biology from the University of Chicago
and an MS in Human Physiology from Georgetown University. He graduated
from the Medical College of Virginia, where he also completed his
Internship and Residency in Internal Medicine. He served as a Fellow
of Allergy and Immunology at Barnes-Jewish Hospital and Washington
University at the St. Louis School of Medicine.
He is Board Certified in Internal Medicine and in Allergy and Immunology.
Dr. Moss is on staff at Sentara Norfolk General Hospital, Sentara
Leigh Memorial Hospital, Bon Secours De Paul Hospital, and Chesapeake
General Hospital.
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