Baby
FOOD ALLERGIES: THEY'RE NOT AS COMMON AS YOU THINK
By Michael G. Marcus, M.D.
Food allergies are a very common concern among parents. In recent
polls, up to 25 percent of parents felt that their children suffered
from food allergies. However, when their children were tested only
around 5 percent of them were proven to have true food allergies. Why
is there this great discrepancy between parental perceptions and actual
facts?
For starters, it's easy to blame every rash or hive on a food
allergy. And while a food allergy can cause these symptoms, skin
reactions are very common in children and can be triggered by a variety
of other causes, such as viral infections, harsh soaps, medication, and
topical irritants. Only careful testing can accurately isolate the true
cause of the reaction.
Other common symptoms of food sensitivity can include abdominal
pain, nausea and diarrhea. But again, other causes may also be the
culprit. A viral infection of the gastrointestinal tract can frequently
cause the above symptoms and actually damage the intestines to the
point where a two to four week recovery period is needed for complete
healing. In this case, a child may have difficulty digesting certain
foods, such as milk, until the intestine is fully healed. Additionally,
lactose intolerance, a condition where the body lacks a enzyme needed
to properly digest milk products, can also cause these same symptoms.
Finally, nasal congestion, cough and wheeze can occasionally be
caused by food allergies, however many other exposures-such as contact
with ragweed or pollen-can also result in these same symptoms.
Testing
The key to identifying a true food allergy is testing. Three
different types of allergy tests are available to accurately identify
the food (if any) responsible for the reactions. Skin tests have been
used for more than 80 years to pinpoint allergy triggers. These tests
are performed by introducing a minute quantity of purified food extract
under the skin and observing the reaction after twenty minutes. This
test is felt to be 80 to 95 percent accurate.
More recently, a blood test called Radioallergosorbent (RAST) has
been used as an alternative to skin testing. The advantage of RAST is
that it requires only one to two vials of blood through one needle
stick, rather than the 20 or more scratches used in skin testing. The
disadvantage is that it is only 80 percent (at best) accurate in its
results.
The "gold standard" for testing is a double-blind food challenge. In
this test, the patient eats a capsule containing a small quantity of
concentrated food without knowing what food is being eaten. If the
patient develops the same reaction after two to three challenges with
the same food then it is considered a true positive reaction.
Treatment
Once the offending food is identified, the only acceptable treatment
is total avoidance of the food. No other treatment will effectively
prevent reactions. Antihistamines can be helpful to relieve symptoms,
however, as they wear off the symptoms will frequently return. If the
responsible food is avoided for six months to two or more years, then
your child will likely be able to tolerate the food when it's
repeatedly reintroduced.
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About The Author
Michael G. Marcus, M.D. is Director
of Pediatric Pulmonology, Allergy & Immunology at Maimonides
Medical Center in Brooklyn, New York.
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