A Vignette
A 22-month-old previously healthy girl was brought to the emergency
room in respiratory distress. She had been well until the day of
presentation. Shortly after disembarking from an airline flight, she
developed cough with one episode of emesis. En route to the emergency
room, her breathing became labored and she developed hives. She was
diagnosed as having an allergic reaction and treated aggressively with
IV methylprednisolone, IV diphenhydramine, inhaled albuterol, and
oxygen. Mechanical ventilation was not required and her symptoms
improved rapidly. She was monitored in the emergency room for an
extended period and discharged in stable condition with a prescription
for diphenhydramine and methylprednisolone solutions. No specific
allergen was identified. She was seen by a pediatric allergist where
she was found to have a 6 mm response to peanut on skin prick testing,
and a peanut-specific IgE level of 52 kU/L. She was diagnosed as
having severe peanut allergy and avoidance was strongly recommended.
Discussion
Peanut allergy affects between 0.4 and 2.0% of children. Prevalence
has been increasing in recent years, but the reason for this increase
is not well understood. If reactions are identified immediately,
treatment is usually effective. Despite this, about 200 people die
each year from peanut reactions. Biphasic reactions, in which the
initial reaction subsides, but then recurs within a few hours, are
common. The second portion of a biphasic reaction is often less
treatable. Because of this risk, patients should be monitored for at
least 4 hours after a reaction. Patients who successfully treat their
own reactions with subcutaneous epinephrine should still seek medical
attention, again to monitor for biphasic reactions.
The gold standard for diagnosis is a double blind placebo controlled
food challenge (DBPCFC), but this is rarely done. A diagnosis can
usually be reliably made with clinical history, skin prick testing and
a peanut-specific IgE blood test (psIgE). A skin prick test involves
pricking the skin with a needle that is exposed to peanut extract and
measuring the allergic rash that develops. The psIgE blood test
measures the amount of antibody against peanut proteins. The higher it
is, the more allergic the patient is. A positive skin test or psIgE is
not sufficient for the diagnosis. Some type of reaction to peanuts is
required (either spontaneous, or via monitored food challenge).
Peanut allergy was previously felt to be permanent, but recent
evidence documents that 20% of children outgrow their allergy. More
than 60% of patients with an psIgE level of less than 5 passed a food
challenge. IgE levels correlate inversely with likelihood of
resolution, but this correlation is by no means perfect. Some patients
with undetectable psIgE levels will fail a challenge, while some
patients with very high psIgE levels will pass. One expert recommends
waiting until the age of 4 to consider a challenge, and to use a
cutoff psIgE level of less than 5 kU/L in most patients. Recurrence
of peanut allergy after resolution is rare, but is associated with the
lack of regular peanut intake after resolution of the allergy.
Controversy exists regarding risk factors for developing peanut
allergy. The AAP initially recommended that peanut not be introduced
early in a child’s life, but rescinded that advice given the lack of
evidence behind it. This leaves a void for parents as there is no
recommendation to withold or introduce peanuts to toddlers. It is also
not clear if maternal peanut intake during pregnancy or breast feeding
increases the risk of developing peanut allergy in children. Studies
have been conflicting, so more definitive studies are underway. No
evidence-based advice can be given one way or the other to pregnant or
breastfeeding women, but at the minimum, there is no good evidence to
support avoiding peanuts.
The mainstay of treatment is education. Parents should be taught not
only how to identify peanuts in foods, but to identify situations
which are high-risk for exposure to peanuts. Avoidance of buffets,
ice-cream parlors, and bakeries is recommended because the risk of
cross-contamination in those setting is high. Religious reading of
food labels is important. Patients who are allergic to peanuts are
often also allergic to tree nuts, despite the dissimilarity in those
food types. Highly refined peanut oil is usually NOT a risk, but
cold-pressed peanut oil is not safe.
Most importantly, an epi-pen should be carried at all times and extra
doses should be left at daycare facilities and schools. All caregivers
should be comfortable giving an epi-pen injection and this should be
provided at the first sign of a systemic allergic reaction. Waiting to
give diphenhydramine or other therapies a “chance to work” can be
dangerous. Follow a Food Allergy Action
Plan
Over 80% of people who died from allergic reactions were not given
appropriate instructions on how to prevent future reactions. Most
mortality occurs because of late treatment. If you take one thing away
from this long post, keep an epi-pen handy and use it liberally.
Trials are underway investigating various oral-based immunotherapies,
but none are strongly recommended at this point. Injection
immunotherapy has not been found to be useful.
Personal Comment
So, the 22 month old above is Anika and she gave us the scare of our
life a couple years ago. The scary part now is that we never saw her
actually eat a peanut, so we’re especially vigilant now. Fortunately,
Anika seems to understand the importance of avoiding peanuts. When she
was diagnosed, I did some research but never documented my notes. She
recently had another allergist appointment, so I reviewed those notes
and any new data. I figured I should write up my notes so I wouldn’t
have to review this again from scratch every year. I didn’t intend it
to come out so ‘medical-speaky’, but there it is. Anika and Kavi are
sitting next to me as I write this and they want to give some
information to you, too.
Kavi says:
“Always ask at the restaurant if things have peanuts and make foods
at home that do not have peanuts. Always check if there are peanuts in
every food you eat.”
Anika says:
“We might have to go to the doctor if we eat peanuts. If I eat
peanuts by accident, my teacher will give me a Happy-Pen (epi-pen).”
References
- Sampson HA. Peanut Allergy. N Engl J Med, 2002;346;1294-8.
http://www.nejm.org/doi/full/10.1056/NEJMcp012667
- Fleischer DM, et. al. The natural progression of peanut allergy:
Resolution and the possibility of recurrence. J Allergy Clin
Immunol, 2003;112;183-9.
http://www.jacionline.org/article/S0091-6749(03)01251-X/abstract
- O’B Hourihane J. Peanut Allergy. Pediatr Clin N Am, 2011;58;445-57.
http://www.pediatric.theclinics.com/article/S0031-3955(11)00006-X/abstract
- Rinaldi M, et. al. Peanut allergy diagnoses among children
residing in Olmstead County, Minnesota. J Allergy Clin Immunol, 2012:130:945-50.
- Burks AW. Early peanut consumption: postpone or promote? J Allergy
Clin Immunol. 2009:123:417-423.
http://www.jacionline.org/article/S0091-6749(08)02436-6/fulltext
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Here’s a
medline feed URL
that I monitor which should show new studies or reviews related to
this topic.
