Atopic or Allergic
Allergies change as one grows older. Often a child first develops
Eczema, then Food Allergy, Asthma and Rhinitis. Many will outgrow
Eczema, Food Allergy and Asthma by age 15 years. (Barneton & Rogers
BMJ 2002, 324. 1376-9).
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evidence for the prevalence and management of food allergy is
greatly limited by a lack of uniformity for criteria for making a
Eczema - Peak age 1
month, subsides by 5 years.
Food Allergy - Peak
age 1 to 3 months, subsides by 14 years, but some may have
symptoms into adulthood.
Asthma - Peak age 5
years, subsides by 14 years, but some may have symptoms into
Allergic Rhinitis -
Peak age 8 years, persists throughout adulthood.
May be mediated by IgG or IgE antibodies. Skin testing is only for IgE. Challenge testing with the food is the best way to diagnosis.
IgE stimulates the mast cell and releases Histamine and to a lesser
degree Platelet Activating Factor (PAF). IgG stimulates the
macrophage and releases PAF. Both PAF and Histamine increase
vascular permeability and can cause anaphylaxis.
prevalence and even the diagnosis of food allergy is limited by the
lack of uniform criteria for making the diagnosis.
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other words, what is and is not a food allergy will differ between
physicians and patients may be over diagnosed. Many
patients and the public overestimate the presence of a food allergy.
Reactions which may
mimic food allergies:
Food mixers that
wear latex gloves: Sushi, Sandwich and Sub Shops, etc. The customer can
react to the Latex.
Flour can contain
contamination with dust
Fish can be
infected with bacteria. Proteus breaks down fish muscle and
Young infants have an
increased risk of food allergy – anything which prevents breakdown of
food in the gastrointestinal tract (stomach and intestines).
GI tract not
mature. Newborns have decreased enzyme (proteolytic) activity in
the gastrointestinal tract, an immature (underdeveloped microvilli) lining and
lack of IgA and IgM in gut (exocrine) secretions. Some recommend
not introducing solid foods till 4 to 6 months of age.
Use of antacids.
Birth by C-section
prevents the baby from picking up mom’s flora (bacteria)
which helps break down food.
during pregnancy and lactation.
Peanut allergy is a common and the most severe food allergy. 70% of
peanut allergic children react to the first ingestion of peanuts. In
these cases, the infants have been previously exposed to peanuts
possibly by mother’s milk or by cutaneous contact with the peanut
The initial reaction does not predict the severity of future
reactions. 52% will develop potentially life-threatening symptoms –
throat tightness and angioedema, wheezing, chest tightness, noisy
breathing, increase in heart rate. (Vander Leek TK, et al. J Pediatr
35% of peanut allergic children will cross react with another tree
Other common food allergens which can cause severe life
threatening reactions (anaphylaxis) are: Tree nut, seafood, finfish,
milk, and eggs. Food additives are also common – carmine, spices and
food gums. Reactions can also occur from benzoates used in diet soft
drinks and canned vegetables, monosodium
glutamate (MSG) on salad bars in restaurants and
(Vaseline Intensive Care Lotion). Health foods have also
been reported to cause reactions. There have been three reports of
anaphylaxis to bee pollen. Many reactions to “Bird Nest” soup.
Food – Food Cross Reactions: (Sicherer SH, Cross Reaction
JACI 2001; 108:881-890)
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Peanut - 59% will
cross react to hazelnuts or brazil nuts. (Also, in allergic
patients between 23% to 50% to other nuts.)
Walnut - 37% will
react with cashew and
Wheat - 20% will
react with another grain
Fish - 50% chance
of reaction with another fish
Shell fish - 75%
will cross react to another shell fish
Cows milk -- 92%
will cross react to goat's milk but only 4% with horse
banana -- 11 % will cross react with latex
Pollen –Food Cross
This can occur with
cross reaction to antigens in fruits and vegetables. Cooking may
Pollen (birch and
ragweed) -- 55% will react with apples, peaches, honeydew etc.
Diagnosis of Food
(Remember this only tests for IgE reactions.):
testing (shots) is not recommended (Intradermal testing is
not paid for by
Skin Prick testing:
Good for telling what you are NOT allergic to but not what
you ARE allergic to (low positive predictive accuracy, good
negative predictive accuracy). (Skin prick testing is not
paid for by Medicare.
and eggs, the testing results are approximately 50%
false positive but less than 5% false negatives. For
peanuts, 70% false positive and 10% false negative rate.
No correlation between skin test size and severity of
reaction. (Sporik R, et al. Clinical Exp Allergy 2000;
testing to nuts – 46% of those tolerant to nuts had a
positive skin prick test as only 0.5% of those
clinically allergic to nuts had a negative test. (Clark
at, Ewan PW. Clinical Exp Allergy 2003; 33 1041-45)
CAP RASTs (ImmunoCAP
Specific IgE blood test): This
test also measures IgE reactions. (This test is also not paid for by Medicare.) Of
patients who had a clear nut allergy, 22% had a negative CAP RAST test compared to 0.5% who were negative to Skin Prick
Testing. Where patients tolerated nuts, 40% had a positive
CAP RAST compared to 46% who had a positive skin prick test (Clark at, Ewan PW. Clinical Exp Allergy 2003;
Is the gold standard. (Approximately 3% false negatives and 1%
false positive.) Best to go on an elimination diet then
challenge. This produces the most marked reactions. Eliminate
all processed foods since allergy to additives are common.
Caveman diet is best. Only eat things that can be gathered or
killed. Nothing processed. Food groups to be rotated during
testing are as listed below:
Proteins - meats
Grains - Rice,
wheat, corn, oats, barley
Vegetables - Yellow, green, potatoes
Petroccione T (Lancet 2001 358:1871-1872) found a false negative rate
of approximately 3% and a false positive rate of less than 1% to
food challenge testing in children.
Rarely outgrown. But may outgrow if the initial reaction
involves only the skin (Skolnick HS et al. JACI
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Soy, wheat, egg,
milk - frequently outgrown.
is to avoid exposure. Some research is being done on desensitization
to milk and other foods. You must know how to handle a reaction. Ask
your doctor for guidelines and many physicians will prescribe and
teach patients on how to use an epi-pen injection device.
Fatal Food Reactions: The majority of patients knew of the
allergy but had accidental exposure. Patients with asthma were at
higher risk. (Bock SA, et al. JACI 2001, 107: 191-3) Of 32 cases of
fatal anaphylaxis the causative agent was identified as:
Peanut - 20
Tree Nuts - 10
Milk - 1
Fish - 1
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