Food allergy in children

Allergy medicine
Food allergy in children
Diagnosis, treatment, support, and education
By Nancy Ott
Food allergies are on the rise in the United States. An estimated 6 percent of
Americans have a food allergy, and studies in the U.S. and Canada have shown
that peanut allergies have doubled in the last decade. It has been reported that
nearly one­third (30 percent) of the population think they or their children have a
food allergy, though they may instead have adverse food reactions rather than a
true food allergy. Adverse food reactions can vary from aversions and
pharmacologic effects to idiosyncratic reactions, as well as other immunologic
reactions.
Food allergies can be classified into those that are IgE mediated and those that
are non­IgE mediated. In IgE­mediated food allergies, allergen­specific IgE
antibodies are produced in the body in response to exposure to a food allergen,
usually a protein. They are the most severe form of food allergies, are typically
rapid in onset, and may lead to anaphylaxis. Non­IgE­mediated food allergies
tend to become evident hours to days after allergen ingestion, and usually
manifest in the gastrointestinal tract.
Though a number of hypotheses have been put forth to explain the rise in food
allergies, no one knows for sure why the increase is occurring. We do know that
90 percent of food allergies are caused by eight foods: milk, egg, soy, wheat,
peanut, tree nuts, fish, and crustaceans. The most common food allergy for
adults is fish and crustaceans, followed by peanut and tree nuts. Infants and pre­
school children are more commonly allergic to milk, egg, soy, peanut, and wheat.
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An estimated 60 percent to 80 percent of children will outgrow food allergies by
their teenage years, with the exception of allergy to peanut, tree nuts, fish, and
crustaceans.
Symptoms and diagnosis
Symptoms of food allergy reaction range widely, from mild atopic dermatitis
(eczema), hives, and gastrointestinal symptoms to anaphylaxis and death.
Anaphylaxis can occur with the first ingestion of the food, or the first reaction
may be mild and the next one anaphylaxis. Up to 30 percent of 32,000 or more
emergency room visits per year for anaphylaxis were caused by food reactions,
according to a Mayo Clinic study. The most common food that causes deaths in
the U.S. is peanut (200 deaths), followed by tree nuts, fish, and crustaceans.
When should a health care provider consider a referral to an allergist for a
possible food allergy? If a young child has severe eczema or atopic dermatitis or
a patient of any age develops hives, swelling, vomiting, diarrhea, or anaphylaxis
within an hour or two of eating a specific food, an allergist can help with
diagnosis, treatment, and prevention. An allergist can also help rule out a food
“allergy” that isn’t present.
Diagnosis of IgE­mediated food allergy is based on a history of a relatively rapid
reaction to the food—within minutes to one to two hours after ingestion or
inhalation. Physical examination is especially helpful if the patient is seen during
the allergic reaction, as later the exam may be normal. Blood testing can be done
using immunoCAP methodology (previously known as RAST).
When it comes to interpretation of tests for food allergy, foods are not created
equal. Hugh Sampson, MD, director of the Jaffe Food Allergy Institute at the
Mount Sinai Medical Center, N.Y., and others have established food probability
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curves for different foods. For children under the age of two years, a peanut level
>5.0 kU/L statistically has a 90 percent­plus probability of a reaction. The level
does not predict severity of the reaction, however. For children over the age of
two years, the level jumps to 14.0 kU/L for a greater than 90 percent chance of
reaction to peanut. Probability curves have also been published for egg, milk,
some tree nuts, fish, soy, and wheat (JACI, Aug. 2004).
Skin testing can also be done and is slightly more sensitive. If a food allergy is
suspected and the immunoCAP test is negative (< .35 kU/L), a skin test will pick
up the 20 percent or so allergic people that the immunocap missed. The size of
the reaction is measured in millimeters. Studies aimed at correlating the size to
probability of reaction similar to immunoCAP levels are ongoing.
Treatment and management
Currently the only treatment for food allergies is avoidance. Each stage of a
child’s life presents different concerns and problems in management of food
allergies.
Infants. For infants, parents have to educate day care providers about what their
child can eat, cross­contamination issues, and cross­reactive foods, as well as
making sure other children won’t have the allergenic protein on their hands or
clothes or in their mouth if they are in contact with the allergic child.
Toddlers and pre­school­age children. In the toddler and preschool years,
children are more autonomous and can inadvertently eat a food that they
shouldn’t have, for example, by picking up a food they find on the floor or on a
table. Other children also are a danger to them. Another child with a peanut
butter sandwich can share or spit the food or lick the allergic child, causing the
child to ingest or inhale food particles that may cause a reaction.
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A recent study looked at whether or not allergenic food such as peanut butter
would cause a reaction if the allergic child had peanut butter on his or her skin or
smelled it in the absence of aerosolized particles (i.e., dust from peanut shells or
boiling the food). The good news was that severely allergic patients only
developed hives at the point of contact and did not develop a more severe
reaction as long as the food did not get into their mouth or eyes. Smelling the
food alone did not cause any reaction. However, boiling the food can cause
protein particles to aerosolize and cause a reaction? and walking on peanut shells
can disturb the peanut dust and aerosolize the particles.
Grade school through high school. As children age and attend grade school
through high school, their ability to recognize a potential ingestion or reaction
should increase. Other students around the allergic child may also be able to
learn how to help the allergic child avoid a food. Parents’ anxieties may increase
as they experience less control over where the child is and what he or she eats.
Another concern is that teenagers are more likely to experiment and to feel
invincible (“nothing can harm me”). Studies have shown that anaphylaxis and
death from food allergies increase in the teens to early adulthood. Children in
this age group also are less likely to carry their epinephrine with them.
Patient education
Because almost every food­allergic patient has an accident at some point, it is
critical that these patients learn how to use an epinephrine­containing device
such as Epi pen or Twinject and routinely carry it with them. To learn proper
administration techniques, patients can use special practice devices (i.e., without
needles) or practice shooting an expired device into an orange. Because peanut,
tree nuts, fish, and crustaceans are the foods that most commonly cause
anaphylaxis and life­threatening reactions, epinephrine should be used early if it
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is recognized that the food­allergic person ate food containing one of the
“culprit” foods.
Regardless of the food type, if anaphylaxis has occurred in the past, epinephrine
should be given before a reaction occurs if the food allergen has been ingested or
inhaled. It is recommended that after using epinephrine, the patient or caregiver
call 911 for observation and/or further treatment of the current reaction or in
anticipation of a possible biphasic reaction. Five percent to 10 percent of patients
may experience a biphasic reaction within 4 to 72 hours after a reaction, and it
may be worse than the first reaction.
Additional medications may be given after epinephrine, such as histamine­ type­
1 receptor blockers and, sometimes, histamine­type 2 receptor blockers to
augment the histamine­type 1 blocker. Prednisone is often given as well,
although no placebo­controlled studies exist. Patients having a severe reaction
should have their legs elevated to assure adequate blood flow to the heart. IV
fluid management, pressor drugs, and intubation equipment should also be
available in clinics, ambulances, and hospitals.
Support and resources for families and caregivers
Because food allergy symptoms are not stereotypical (particularly with peanuts,
tree nuts, and fish/crustaceans) and anaphylaxis can occur with the first
ingestion of the food, having a child with a food allergy is very stressful for
families. Support through national and local organizations, as well as an
allergist’s guidance, can help patients and families cope with the challenges of
food allergies.
FAAN (Food Allergy & Anaphylaxis network, www.foodallergy.org) provides
useful information on managing the difficult task of avoiding the foods that may
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cause their children to become very ill. The Food Allergy Initiative
(www.faiusa.org/) carries information about food allergy research.
Locally, the AFAA (Anaphylaxis & Food Allergy Association of Minnesota,
www.minnesotafoodallergy.org) advocacy organization holds monthly meetings
and other events to educate and support people with food allergies. Each spring,
AFAA sponsors a daylong seminar in Minneapolis with local and national food
allergy experts. Information is available at www.minnesotafoodallergy.org.
National food­labeling laws have also helped patients and families dealing with
food allergies. The Food Allergen Labeling and Consumer Protection Act
requires food manufacturers to disclose whether products contain any of the top
eight food allergens. The law, which took effect Jan. 1, 2006, mandates that the
labels of foods containing milk, eggs, fish, crustacean shellfish, peanuts, tree
nuts, wheat, and soy declare the allergen in plain language on the ingredient list.
However, there are still areas of confusion about whether the food is safe or not,
particularly when the food was processed on the same equipment or in the same
facility as the food allergen. Studies have suggested that foods processed on the
same equipment often contain the food allergen. Legislators are working on
making the labeling more understandable and straightforward. More
information about current legislation and labeling can be found on the FAAN
Web site.
Efforts to improve testing, treatment
Although the vast majority of the U.S. population can eat foods without fear of
death, for some people this fear is an everyday reality. Ongoing studies are
working on desensitization protocols for egg, peanut, and tree nut allergies.
Vaccine studies in mice are under way. Better testing may be available to sort out
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the truly allergic patients from false­positive results that are common in atopic
patients.
Perhaps in 20 years a cure will be available and we won’t have to worry about
food allergies. Until then, knowledgeable health care providers can help patients
to receive the best care possible for this malady.
Nancy Ott, MD, practices at Southdale Pediatric Associates, LTD, specializing in
Adult & Pediatric Allergy & Asthma. She is the current president of the
Minnesota Allergy Society.
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