Food Allergy & Asthma Redux

Abstract

Source: Liu AH, Jaramillo R, Sicherer S, et al. National prevalence and risk factors for food allergy and relationship to asthma: results from the National Health and Nutrition Examination Survey 2005–2008. J Allergy Clin Immunol. 2010; 126(4): 798– 806; doi: 10.1016/j.jaci.2010.07.026Investigators from multiple institutions reviewed data from the 2005–2006 National Health and Nutrition Examination Survey (NHANES) to estimate the rates of food allergy (FA) in the United States, identify populations at high risk for FA, and explore the associations with other atopic conditions. Serum specific IgE food panels (peanut, cow’s milk, egg white, and shrimp) were obtained on 79.3% of the 10,348 participants. Based on specific cut-offs for IgE levels against each food, participants were classified as having unlikely FA, possible FA, or likely FA. Clinical FA rates were estimated by summing 50% of the number of participants with possible FA and 95% of those with likely FA. A classification of “sensitization” was made in study participants who had an IgE level above the lower limit of detection for at least one food allergen. Participants were considered to have other atopic conditions, including asthma, hay fever, and eczema, based on self-report and doctor-confirmed diagnoses. Both the sampling and analytical methodologies were designed to provide nationally representative estimates.Among the diverse group of study participants, allergic sensitization to at least one food allergen was identified in 16.8% of those enrolled. The rate of asthma in the study population was 14.6%, hay fever 10.8%, and eczema 9.1%. The overall national prevalence of clinical FA was estimated to be 2.5%; estimates for clinical FA to milk, egg, and peanuts were 0.4%, 0.23%, and 1.3%, respectively. Rates of clinical FA were highest in children aged 1 to 5 years, at 4.2%, and lowest in adults over 60, at 1.3%. The prevalence of clinical FA to milk, eggs, and peanut were each about 1.8% in children aged 1 to 5 years, while the rates of peanut allergies were highest in children aged 6 to 19, at 10.7%. Rates of allergy to multiple foods were highest in children aged 1 to 5 years, at 0.4%.The risk of possible or likely FA was increased in non-Hispanic blacks (OR=3.06; 95% CI, 2.14–4.36), males (OR=1.87; 95% CI, 1.32–2.16), and children (OR=2.04; 95% CI, 1.42–2.93). Study participants with doctor-diagnosed asthma also had increased risk of food sensitization. Those with likely FA had an adjusted OR for current asthma of 3.8 (95% CI, 1.5–10.7); emergency department visits for asthma were notably increased in those with likely FA (OR=6.9; 95% CI, 2.4–19.7). In general, FA was more prevalent in individuals living in poverty and least prevalent in those with higher household incomes. The authors postulate that unrecognized FA may contribute to the severity of asthma.Dr Nimmagadda has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.FA prevalence has been rising in the United States over the past decade. Substantial increases in peanut and tree nut allergy have been well documented during this time period.1 Specific risk factors for the development of FA have not been well established. The results of the current study reinforce the concept that male subjects and children are at highest risk for the development of FA. Surprisingly, an increased risk was found in non-Hispanic black individuals as well.Associations between atopic dermatitis and FA have been well established.2,3 However, the association with the development of asthma in children with FA has only recently been documented. The asthma predictive risk index has included FA as a risk factor for the development of asthma in wheezing children younger than 3 years of age.4The authors of this study also point out that the presence of FA may potentially increase asthma severity. Foods in general were not thought to contribute to asthma exacerbations. However, they may play a larger role than previously thought.Asthma is present in nearly all subjects who have fatal anaphylactic reactions to food exposure.5 In food-allergic children with worsening asthma symptoms, the exposure to small amounts of foods can increase bronchial hyperreactivity without inducing bronchospasm.6 Thus, pediatricians should be aware of worsening asthma symptoms in food-allergic children despite adequate asthma therapy. Reinforcing food avoidance should be undertaken at each visit in children with both FA and asthma.