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Thursday, November 7, 2013
The increased incidence of allergies of all types - including peanut allergy - has prompted speculation on their cause. Some scientists believe that the eradication of many infectious and communicable diseases may have affected the immune system. Others believe that improved hygiene practices also may alter the immune system and predispose individuals to the development of allergies later in life. Whatever the cause, enforcing parental adherence and student compliance with peanut-free policies as well as school response readiness to allergic reactions demand knowledge established in research to avoid an over-prudent protocol, cynicism, and apathy, as well as needless panic. Here are some important facts about peanut allergy, diagnosing symptoms and reactions, and recommended management.
Peanuts contain 200 milligrams of seven identified proteins that serve as allergens. In protein doses as low as 100 micrograms (one-tenth of one milligram), subjective complaints of tingling, rhinitis and itching have been reported. In doses as low as 20 milligrams (one-tenth the load of allergens in a typical peanut), allergens stimulate the immune system, which results in the production of large amounts of immunoglobulin E (IgE). Millions of IgE antibodies circulate in the blood and bind to mast cells and basophils present in the gastrointestinal tract, skin and lungs. Basophils and mast cells produce large amounts of histamine, prostaglandins and leukotrienes. These substances are responsible for the allergic reaction that occurs wherever the mast cells and basophils exist. Thus allergic manifestations occur in the respiratory, gastrointestinal, cardiovascular and cutaneous tissues. The IgE-mediated (late-phase) adverse reaction to peanuts can occur immediately or after a few hours. Most responses occur from ingestion, but in rare cases of hypersensitive individuals, touch or inhalation of allergens may produce the allergic response. Severity of reactions depends on which and how many systems are involved and upon the amount of peanut protein exposure.
The first allergic response to peanuts usually occurs between 14 and 24 months of age. Of these, 89% have reactions involving the skin, 42% have respiratory symptoms, 26% gastrointestinal involvement, and 4% cardiovascular involvement. Of the 1.3% of children who experience peanut hypersensitivity, 50% endure one-system involvement, 30% two-system involvement, 15% three system involvement and 1% four-system involvement. Those with multiple system involvement and concomitant asthmatic conditions have poorer clinical outcomes. Interestingly, 70% of these first-time responses occur at the first known exposure. While research has not established a clear link between peanut allergen exposure during intrauterine life or breastfeeding and sensitization, it seems prudent for mothers to avoid peanut ingestion during subsequent pregnancies and during the breast feeding period when older siblings have confirmed peanut allergy.
Diagnosis of peanut allergy is confirmed with the detection of peanut specific IgE via a standard prick test or fluoroenzyme immunoassay. The standard prick test is a skin test that introduces a diluted extract of peanut proteins into the skin. A positive reaction is seen within 15 minutes in the form of a red bump similar in appearance to a mosquito-bite. Many young children have negative responses to the skin test even when they have a true peanut allergy.
Two primary blood tests used for peanut allergy testing are the radioallergosorbent test (RAST) and the enzyme-linked immunosorbent assay (ELISA). As with skin testing, many false negatives are reported. There are two primary reasons for false negative results. First, the prick test extract is very vulnerable to rapid deterioration, and peanut proteins disintegrate easily. Second, the quality of allergy testing equipment has less than 10% internal reproducibility, the World Health Organization standard.
A number of longitudinal studies have monitored children through several years to determine the onset of sensitivity to peanuts and other allergens using IgE antibodies as predictive biomarkers for inhalant allergies. Food allergies had a negative predictive value of 90% in one study. Another study concluded that utilizing the sum of antibody levels in combination with the number of positive allergies represents a more efficient diagnostic tool than the single IgE measure. Another study investigated children with known food and airborne allergies and used atopic dermatitis (rash) as a marker. Findings were that many food allergies resolved over time, but that peanut allergy remained persistent, a fact that cannot be ignored.
The prevalence of peanut allergy has increased significantly in the past thirty years. It is important to know that this is not a food allergy a child typically outgrows as is the case with many other food allergies. School nurses play a pivotal role in helping teachers, administrators, parents, and children to understand allergic food reactions as well as the importance of peanut allergen exposure control. In addition, schools rely on their nurses to provide sound guidance in the development and implementation of school-based exposure control measures as well as emergency preparedness for responding to allergic reactions when they occur. Such thoughtful, science-based plans protect the health of children while also limiting school liability.
Jill F. Kilanowski, MSN, RN, CPNP, Doctoral Student: Health Disparities, College of Nursing, The Ohio State University
Ann Stalter, MS, RN, Doctoral Student: Community Health, College of Nursing, The Ohio State University
This article is a NetWellness exclusive.
Last Reviewed: May 02, 2007
Professor of Clinical Nursing
College of Nursing
The Ohio State University