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

1. Sampson HA. Peanut Allergy. N Engl J Med, 2002;346;1294-8. http://www.nejm.org/doi/full/10.1056/NEJMcp012667
2. 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
3. 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
4. Rinaldi M, et. al. Peanut allergy diagnoses among children residing in Olmstead County, Minnesota. J Allergy Clin Immunol, 2012:130:945-50.
5. 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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