Encyclopedia of Health and Medicine

food allergies 261
Symptoms and Diagnostic Path
A hypersensitivity reaction to a food produces
symptoms that may include
• itching and swelling around the face, on the
lips, and in the MOUTH
• nasal congestion
• wheezing or difficulty BREATHING
• sensation of a lump in the THROAT
• gastrointestinal PAIN (resulting from swelling in
the intestinal mucosa)
• moderate to extensive diarrhea
More generalized symptoms such as SKIN rash,
hives (URTICARIA), and ANGIOEDEMA are also possible.
Symptoms may occur within minutes to 2
hours after eating the food. Anaphylaxis may
develop with any hypersensitivity reaction, even
when previous reactions have been mild.
ANAPHYLAXIS is a medical emergency
that requires immediate treatment
from a doctor. Tingling and swelling of
the lips, tongue, and THROAT 20 to 60
minutes after eating a food for which
there could be an allergy are possible
indications of anaphylaxis.
When there is a clear connection between a
specific food and a hypersensitivity response,
identifying the allergen is fairly straightforward.
When the connection is not clear, the diagnostic
path can be arduous and may include
• blood tests to measure IMMUNOGLOBULIN E (IgE)
levels
• ALLERGY TESTING with suspect substances
• elimination diet
The elimination diet involves removing suspected
foods or foods that are common allergens
from the diet, usually for two weeks, and then
reintroducing them one at a time until symptoms
recur. The last food reintroduced is the likely
allergen. An elimination diet is appropriate only
for people who have mild to moderate hypersensitivity
reactions. The risk for anaphylaxis is too
great to use the elimination diet approach in people
who have had severe allergy symptoms such
as wheezing, breathing difficulty, or urticaria
(hives). No single diagnostic approach works for
all food allergies; diagnosis becomes a process of
drawing conclusions based on symptoms.
COMMON FOOD ALLERGIES
cow’s milk
eggs
peanuts
shellfish (lobster, shrimp, crab)
soy
strawberries
tree nuts (almonds, wheat (including flour)
cashews, walnuts, pecans)
Treatment Options and Outlook
A moderate hypersensitivity reaction may require
treatment with ANTIHISTAMINE MEDICATIONS; a serious
reaction may require a course of oral CORTI-
COSTEROID MEDICATIONS to halt the immune
response and relieve the discomfort of the symptoms.
Many hypersensitivity reactions to foods
produce mild symptoms that go away without
treatment. A doctor should evaluate symptoms
that do not improve within a few days.
The most effective long-term treatment is to
avoid the allergen. This is not always as easy as it
sounds because often variations of the allergen are
ingredients in prepared or baked foods. Peanuts,
eggs, milk, soy, and wheat are common in many
foods. Cross-contamination is also a concern, particularly
among processed foods manufactured in
facilities that use various ingredients in different
products. An ice cream manufacturer may make a
flavor that has nuts, for example, and then use the
same equipment to make a flavor that does not
have nuts. Even residue not visible to the eye can
be sufficient to cause a hypersensitivity reaction in
someone who is highly allergic. Labels on packaged
foods include information about whether the
product comes from a facility in which cross-contamination
is possible. People who have food
allergies must ask about obvious as well as hidden
ingredients when eating away from home.
DESENSITIZATION (allergy shots) is a therapeutic
option for people who have allergies to foods that
are especially common or who have severe hypersensitivity
reactions. Though it takes up to two
years for desensitization to reach its maximum
effectiveness, most people notice a reduced hypersensitivity
reaction within six months.