CME Author: Zeena Nackerdien
Study Authors: Ruchi S. Gupta, Christopher M. Warren, et al.
Target Audience and Goal Statement:
Allergists and primary care physicians
The goal was to learn more about nationally representative estimates of the distribution, severity, and factors associated with adult food allergies.
Study investigators addressed the following questions:
- What was the prevalence and consequences of food allergies among a nationally representative sample of U.S. adults?
- Were there other factors that could be correlated with adult-onset allergy?
Synopsis and Perspective:
Food allergies are immune-mediated adverse events that can be broadly classified as IgE-mediated, non-IgE mediated, or mixed (IgE and non-IgE) reactions. Food allergies have to be distinguished from food intolerances, which are caused by enzyme deficiencies or reactions against certain substances. Symptoms of a food allergy can range from mild to severe, with anaphylaxis being a well-known example of a severe reaction.
While this costly, potentially life-threatening condition has been examined at a population level among children, less is known about the population-level burden of food allergies among adults in the U.S. Neither the CDC’s National Health and Nutrition Examination Survey (NHANES) nor the FDA’s Food Safety Survey collects information about specific allergic reaction symptoms that would enable a differential diagnosis of food allergy from oral allergy syndrome or food intolerance. A literature gap exists with respect to specific features of adult food allergies, such as relative frequency and timing of adult- versus childhood-onset food allergy, allergen type, severity, and key sociodemographic and clinical factors of each of these food allergy characteristics.
Ruchi S. Gupta, MD, MPH, of Northwestern University Feinberg School of Medicine in Chicago, and colleagues, administered surveys to U.S. households from 2015 to 2016. They employed a dual-sampling approach using the non-partisan and objective research organization at the University of Chicago’s (NORC) Amerispeak panel and the Survey Sampling International (SSI) non-probability-based sample. This investigation was an extension of the same group’s 2009-2010 national child food allergy survey, developed by pediatricians, allergists, health services researchers, and methodologists for surveys.
Prevalence and severity of overall and food-specific convincing adult food allergies served as the primary endpoints. A convincing allergy was determined based on a report of one or more stringent symptoms across two or more of the following organ systems: skin or oral mucosa, gastrointestinal tract, cardiovascular, and respiratory tract.
Information regarding actual and self-perceived food allergies were collected from 40,443 survey respondents (mean age 46.6). Gupta and colleagues estimated that 10.8% (95% CI 10.4% -11.1%) of the respondents had a convincing food allergy. Less than half of the respondents (48.0%, 95% CI 46.2%-49.7%) developed food allergies as adults. When stratifying results by age group, food allergy prevalence rates were lower for adults ages ≥60 compared with adults in their 30s (8.8% vs 12.7%). Women were also more likely to report a convincing food allergy (13.8%, 95% CI 13.3-14.4) versus males (7.5%, 95% CI 7.0-7.9).
Shellfish (2.9%, 95%CI 2.7%-3.1%), milk (1.9%, 95%CI 1.8%-2.1%), peanut (1.8%, 95%CI 1.7%-1.9%), tree nut (1.2%, 95%CI 1.1%-1.3%), and fin fish (0.9%, 95% CI 0.8%-1.0%) were identified as the most common allergies. Chronic atopic comorbidity, including asthma, eczema, allergic rhinitis, urticaria, and latex allergy were linked to increased odds of convincing food allergy.
Gupta told MedPage Today that she was surprised to find that almost half of respondents reporting food allergy symptoms consistent with IgE-mediated reactions developed food allergies as adults.
Among food-allergic adults, 51.1% (95%CI, 49.3%-52.9%) had a severe food allergy reaction. Additionally, 45.3%(95%CI, 43.6%-47.1%) of respondents were allergic to more than one type of food.
About 38.3% of respondents with convincing food allergies had reactions serious enough to end up in hospital emergency departments (ED), the authors noted. Among adults with one or more convincing food allergies, only 24% of respondents reported having a current epinephrine prescription.
Gupta said more research is needed to determine if specific environmental triggers play a role in promoting allergic reactions to certain foods among adults who were not previously allergic.
Double-blinded, placebo-controlled oral food challenges is the gold standard for food allergy diagnosis; however this study was based on self-reporting so possible bias was a study limitation.
Source Reference: JAMA Network Open, Jan. 4, 2019; DOI:10.1001/jamanetworkopen.2018.5630
Study Highlights: Explanation of Findings
More than 26 million U.S. adults (10.8%) had at least one current food allergy during the study period. Almost twice that number of survey respondents (19%) believed that they were allergic to food. Collectively, the data suggested that at least one in 10 U.S. adults are food allergic, and almost one in five adults perceive themselves to be food allergic, but only one in 20 adults are estimated to have a physician-diagnosed food allergy. At least 10 million adults received food allergy treatment in the ED during the study time-frame.
In addition, almost half of all food-allergic adults develop at least one adult-onset food allergy, and at least 12 million respondents were estimated to have an adult-onset food allergy, in keeping with findings from another study that reported the common occurrence of this phenomenon.
Shellfish and peanut allergies — conditions that usually persist across a lifespan — were two of the more common allergies in the current investigation. Shellfish allergy prevalence was 2.8% among individuals ages 18-29 years, and 2.6% among those ages ≥60 years. This was a lower rate of decrease across the life span than observed for other food allergies, and an indicator of the enduring nature of this food allergy, according to the authors.
In addition to 7.2 million U.S. adults with shellfish allergies, almost 4.7 million adults were estimated to have milk allergies and 3.0 million respondents were estimated to have tree nut allergies. Egg and wheat allergies were equally common (2.0 million each), followed by soy and sesame (0.5 million each) allergies.
Gupta reiterated that while food allergy prevalence has been well documented among children in population-based studies, less was known about food allergy prevalence in adults.
“There are many other food-related conditions common among adults that may be confused with (systemic) food allergy, such as gluten or milk intolerance or oral allergy syndrome,” she said. “That is why it is so important to get a diagnosis. A good take-home for physicians is that they should ask their patients about this. We routinely ask about medication allergies. It might be a good idea to ask about food as well.”
Gupta’s group also reported that “Hispanic adults were estimated to have comparable rates of food allergy to non-Hispanic black adults, as well as the highest rates of food allergy-related ED visits among all racial groups, despite reporting epinephrine prescription rates comparable to those of white adults.”
“The scope of future work examining food allergy disparities should be expanded to further investigate racial/ethnic differences among Hispanic adults,” they added.
Trends with respect to severity of food allergies were comparable to evidence from the literature, particularly the finding that age correlates with more severe allergic reactions. Among adults with one or more severe physician-diagnosed food allergies, who reported at least one food allergy-related ED visit in the past year, only 65% reported a current epinephrine prescription. Given that food allergies, especially adult-onset food allergies, remain an emerging health issue, the low rate of epinephrine prescriptions should be a cause for concern.
The authors suggested that “adults need to be encouraged to see their physicians to receive proper diagnosis, epinephrine prescription, and counseling for their food allergy.”
Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco