FOOD ALLERGY IN CHILDREN
Category: Child Health
Abstract :
Food allergy - General aspects of food allergy diagnosis and management Food
allergy is frequently encountered in general pediatric practice. The prevalence
of food allergy in children appears to be increasing for reasons that are still
poorly understood. The most important aspect of the care of these children is to
know the clinical features of food allergy and to recognize the limitat
Food allergy - General aspects of food allergy diagnosis and management
Food
allergy is frequently encountered in general pediatric practice. The prevalence
of food allergy in children appears to be increasing for reasons that are still
poorly understood.
The most important aspect of the care of these children is to
know the clinical features of food allergy and to recognize the limitations of
the currently available tests for food allergy, to prevent unnecessary dietary
limitations and anxiety. A recent review and journal supplement summarize
clinical features of these often confusing disorders.
Important points
regarding IgE-mediated food reactions are that the levels of food-specific IgE
predictive of clinical reactivity vary by food and age and the level of
food-specific IgE is not necessarily predictive of the severity of reaction.
Also, as demonstrated in a recent study of carefully conducted food challenges,
the natur of the original reaction should not be assumed to be predictive of the
nature of future reactions. Subsequent reactions can be more severe and involve
different organ systems. Referral to a board-certified pediatric allergist
should be considered for evaluation of these patients for food-specific IgE and
closely observed oral food challenges when indicated. In addition, children with
multiple food allergies may benefit from consultation with a nutritionist
familiar with the management of food allergy and from food allergy support
groups.
Prevalence of peanut allergy among children rising
Peanut and
tree nut allergy are particularly severe and persistent food allergies. Two
recent studies sought to determine the prevalence of peanut and/or tree nut
allergy among children. One of the studies was a followup, random digit dial
telephone survey from a study reported in 1997, which reported 0.4% of children
under the age of 18 years with peanut allergy and 0.2% with tree nut allergy.
The follow-up survey was conducted in 2002 to determine if the prevalence among
children has changed over time. Based on 4855 households participating in the
survey, representing 13,493 individuals in the US, the overall rate of peanut
and tree nut allergy was not significantly changed over 5 years, but the rate of
reported peanut allergy among children doubled to 0.8%. This increase in
prevalence among children is consistent with a study reported from the United
Kingdom. A Canadian cross-sectional study evaluating children in kindergarten to
grade 3 in school classrooms, used questionnaires, testing for peanut-specific
IgE, and oral peanut challenges. Using conservative assumptions, 1.34% of
children were identified as peanut allergic. Clearly the prevalence of peanut
allergy is increasing among children and more effective methods for evaluation
and management must be developed.
Natural history of peanut
allergy
Recent studies have demonstrated that up to 20% of peanut allergic
patients will lose the allergy over time. A more recent study correlating
CAP-RAST measurements of peanut-specific IgE levels with oral food challenge
results demonstrated that, among children under 5 years of age who had
peanut-specific IgE levels < 5kU/L by CAP-RAST testing, around 50% outgrew
their peanut allergy. Recurrence of peanut allergy was reported in two patients
after successful completion of an oral challenge, although only one was
confirmed. Similar recurrences have been reported previously. Careful follow-up,
with determination of peanutspecific IgE levels and oral food challenges when
appropriate, is required to ensure that children are not unnecessarily labeled
as peanut allergic.
Environmental exposures to food allergens
Allergen
avoidance is the only method currently available for preventing food reactions.
Several reports have suggested that accidental exposure to food allergens
through the skin or by inhalation have led to reactions [46–48], although
typically, ingestion is not excluded in these reports. Food reactions occurring
in school have been reported in 18% of food-allergic children participating in a
telephone survey [49]; peanut or tree nut reactions occurring in school have
been reported in 16% of children participating in the US Peanut and Tree Nut
Allergy Registry [50]. These reports have understandably led to great anxiety as
food-allergic children attend daycare centers and schools where peanut allergen
may be present, most typically in the form of peanut butter. To address this
concern, two recent reports have carefully evaluated the risk of reactions from
casual contact with peanut butter and the distribution of peanut allergens in
schools and other environments. In the first study, 30 children highly sensitive
to peanut were exposed cutaneously to peanut allergen, by application of peanut
butter to the skin for 1 minute, or by inhalation, by having subjects breathe 12
inches from a standardized surface area of peanut butter for 10 minutes.
Cutaneous application of peanut butter led to cutaneous reactions in 33% of the
patients in the study, which is not unexpected. Exposure to the skin or
inhalation, however, did not induce systemic or respiratory reactions in any of
the patients in the study. As noted by the authors, the results apply only to
peanut butter and should not be generalized to exposure from roasted peanuts or
other forms. The second study measured levels of the major peanut allergen, Ara
h 1, in simulated environments and in schools and preschools. Following the
application of a large amount of peanut butter to tables or hands, cleaning with
standard cleaning agents led to undetectable Ara h1 levels on the surfaces
(lower limit of detection 30 ng/milliliter). The only exceptions were that with
washing tables with dish soap or washing hands with plain water alone or with
antibacterial hand sanitizer, residual allergen was detected, although at
significantly reduced levels. Samples taken from 6 preschools and schools of
table surfaces, food preparation areas, water faucets, and desks demonstrated
detectable Ara h1 on only 1 of 71 surfaces sampled. These studies are
reassuring; however, continued vigilance must be exercised to ensure careful
cleaning of tables, hands, and other potentially contaminated surfaces and, most
importantly, to prevent accidental ingestion of foods containing food allergens.
Training school personnel on the importance of food allergen avoidance and on
the signs of food reactions and proper administration of epinephrine are
critical areas to be addressed to increase school safety.
Provision
of self-injectable epinephrine to children with food allergy
In addition to
education on food allergen avoidance, all patients with food allergy at risk for
anaphylaxis should be prescribed self-injectable epinephrine devices, instructed
on proper administration, and given action plans that include calling for
emergency transport after administration of epinephrine. Approximately 30,000
anaphylactic reactions to food are estimated to occur in the US yearly with 150
deaths. Reviews of fatal anaphylactic reactions to foods demonstrate that either
delay or failure to administer epinephrine is common in fatal food anaphylaxis.
In one study analyzing 32 fatalities reported to a national registry, only 10%
of the subjects had epinephrine available at the time of the reaction, although
all but one had known food allergy with prior reactions. Among the fatalities in
the registry with sufficient data, most were among adolescents and young adults,
all but one had asthma, and peanut and tree nut were the most common cause. A
recent review highlights many of the issues regarding administration of
epinephrine for anaphylaxis in children, including choosing the appropriate
dose.
Emergency department management of food anaphylaxis
While
guidelines on the importance of prompt epinephrine administration to reverse
anaphylactic reactions have been developed, a recent report demonstrates that
emergency department management of anaphylaxis may be suboptimal. As part of the
Multicenter Airway Research Collaboration, charts of patients presenting with
food allergy in 21 emergency departments were reviewed. Among the patients in
the cohort with severe anaphylactic reactions, only 24% received epinephrine.
Although less than 50% of the patients were diagnosed with the food allergy
prior to presenting with the reaction, only 16% were prescribed self-injectable
epinephrine and 12% were referred to an allergist at the time of discharge.
While it is difficult to determine the reasons for not administering epinephrine
from an emergency department chart review, great effort must be made to ensure
that all caregivers are familiar with guidelines for the treatment of
anaphylaxis and that patients are discharged with self-injectable epinephrine
and instructions for allergen avoidance and follow-up.
Posture and
outcome of anaphylaxis
The posture of patients having anaphylactic reactions
may be important in determining outcome of anaphylactic reactions, as suggested
in a recent letter by an expert in the area of fatal anaphylaxis. In a review of
214 fatal anaphylactic reactions since 1992, a pattern was noticed among cases
of anaphylactic shock occurring outside of the hospital that several deaths
occurred soon after the patients assumed a more upright posture. In several of
the cases with sufficient data, death occurred within seconds of either sitting
or standing. Based on these findings, it is proposed that patients experiencing
anaphylactic reactions leading to collapse or those feeling faint from impending
shock should be kept in a supine position, including during self-administration
of epinephrine. Exceptions are patients with respiratory distress or vomiting.
Although not part of the advanced life support guidelines, it is important to be
aware of these observations.
Anti-IgE treatment for peanut
allergy
Interventions to reduce the risk of anaphylaxis from exposure to food
allergens are needed. In a large, carefully designed, randomized, double-blind,
placebo-controlled study, anti-IgE antibody (TNX-901, Tanox, Inc., USA) was
administered subcutaneously every 4 weeks for 4 doses to patients with peanut
hypersensitivity. Administration of anti-IgE reduced the serum levels of total
IgE and raised the threshold dose for reaction in a dosedependent manner. This
response may be beneficial to prevent reactions from accidental exposures, but
the level of elevation of threshold of reactivity is variable and unpredictable,
depends on regular, long-term administration, and does not reverse the
underlying immune dysfunction. In addition, the antibody (TNX-901) used in the
study is not currently available and Xolair (Genentech and Novartis, USA), which
is approved for use in a subset of patients with asthma, has not been studied
for similar benefits.
Food allergy conclusion
Current research is
focused on identifying diseasemodifying therapies to reverse the underlying
immune dysfunction leading to IgE-mediated food allergy. Until such
disease-modifying treatments are available, strict avoidance of food allergens
and readily available access to self-injectable epinephrine remain the mainstays
of treatment. Families of food allergic children must be educated regarding
recognition of anaphylactic reactions, proper administration of epinephrine,
foods and ingredients to be avoided. Given the complexity of the diagnosis,
evaluation, and treatment of these patients, referral to a board-certified
allergist with expertise in food allergy should be considered. Multidisciplinary
approaches should be considered for these patients to ensure optimal care.
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