Do Food Allergies Increase the Risk of Asthma? Key Questions From a New Study

Sep 20 2016

Do Food Allergies Increase the Risk of Asthma? Key Questions From a New Study

asthma allergyMost of us know that unlucky kid — and some of us were that unlucky kid — who was stuck with more allergies than the rest of the class, from peanuts and eggs to asthma and hay fever. Is it a coincidence that often the kid carrying an inhaler might also be carrying an EpiPen? Many parents and pediatricians have noted anecdotally, and small studies have supported, the idea that food allergies and respiratory allergies tend to occur together. The connection appears to be real, according to a new, large-scale epidemiological study by a multidisciplinary team of researchers at The Children’s Hospital of Philadelphia.

The CHOP team showed that there is an association between food allergies and the risk of asthma and allergic rhinitis. You can read a summary of many of the key findings in the CHOP news release here and the study itself in BMC Pediatrics. To take a closer look, Cornerstone chatted with one of the study’s lead authors, David Hill, MD, PhD, a fellow in the Division of Allergy and Immunology at CHOP, about the many more patterns in allergies across the pediatric population that he and his colleagues were able to detect through their analysis of a large number of electronic health records in the CHOP primary care network. We bring you a rundown of many of the key questions and interesting aspects of the study that parents, physicians, and researchers should know.

What did the study show about associations between food allergies and respiratory allergies?

“Children with food allergy are more likely to go on to develop asthma and allergic rhinitis than those without food allergy,” Dr. Hill said.

The likelihood of developing one of these respiratory allergies was more than double in children who had food allergies in the study, compared to those without food allergies. And the more food allergies a child had, the greater the risk. A child with two food allergies, for example, had a risk of asthma 2.75 times greater, and a risk of allergic rhinitis 3.64 times greater, than a child without food allergies, according to the study data. For a child allergic to four foods, the risks rose even higher, to 5.44 times the baseline risk of asthma and 7.05 times the baseline risk of allergic rhinitis.

But this study could not answer questions about cause and effect. Dr. Hill is confident the finding shows that, for any given child with food allergy, there is a higher than average likelihood that the child will go on to develop a respiratory allergy — not that the existence of a food allergy causes that increased risk.

“I can’t say mechanistically why this is the case, but it’s hypothesis-generating for basic scientists to go back and look at it,” he said.

What did the study show about asthma in the Philadelphia-area study population?

“Asthma rates among Philadelphia children are among the highest in the nation,” Dr. Hill said. About one in five, or 21.8 percent, of children in the study had asthma at some point in their childhood. The study team found these high asthma rates despite the extra scrutiny of their robust methods to avoid potentially overestimating the number of children with asthma.

“Not only did we look at diagnosis codes, but also we went back to the charts and said, are these kids prescribed asthma medications?” Dr. Hill said. Only children who had both a diagnosis code for asthma and a prescription for an asthma medication were counted as having the condition.

The rates of other allergic conditions studied were more similar to previously published rates.

What else was different about the design of this study compared to previous studies on the incidence of allergic conditions?

This was the largest study yet that examined rates of food allergy, asthma, allergic rhinitis, and eczema within a large population of children using diagnosis data from their electronic health records. The researchers used computational methods that allowed them to mine the CHOP Care network going back to 2001. They defined two large groups of children for analysis, including a group of 29,662 patients who had records of care in the CHOP network from within a month after birth and continuing through at least age 5 (known as the birth cohort), and a group of 333,200 children who received care in the CHOP network for at least one year (the cross-sectional cohort).

“These are really huge cohorts,” Dr. Hill said. “They gave us powerful opportunities to find data that wasn’t possible to find previously.”

Another highlight of the study was that its approach was multidisciplinary. Dr. Hill was co-first author of the paper with Robert Grundmeier, MD, a primary care pediatrician and director of Clinical Informatics in the Department of Biomedical and Health Informatics at CHOP, and assistant professor of Pediatrics at the Perelman School of Medicine at the University of Pennsylvania. Jonathan Spergel, MD, PhD, Allergy Section chief at CHOP and professor of Pediatrics at Penn, was the senior author.

What other surprising results stood out about children’s food allergies?

People might perceive peanuts as the top food allergy among children, but the CHOP team found that peanuts’ supremacy does not last. In their cross-sectional cohort, peanuts were indeed the most common allergen among children with food allergies, affecting over 2 percent of the study population up to about age 10. Among pre-teens and teens, the rate of peanut allergies was lower, around 1.5 percent — and in that age group, another allergen surpasses peanuts to take the top position.

“What is unique but has not been as well highlighted is that in 18-year-olds, and presumably into adults, shellfish is the most prominent food allergen, not peanuts,” Dr. Hill said.

That shellfish allergies are relatively common among adults has been known, but the trend in the study population of shellfish rising as the top allergen among teens was surprisingly sharp.

One other surprise: The researchers’ analysis showed that allergy to sesame in this population was more common than previously thought.

“When a kid comes into your pediatric clinic with anaphylaxis after eating a bagel, don’t necessarily assume it’s the cream cheese, but also suspect the sesame seeds on top,” Dr. Hill said.

What comes next? What should pediatricians, parents, and other researchers know?

For parents, recognizing that food allergies come with an associated higher risk of respiratory allergies can help them be attuned to that possibility. They also may find extra motivation to take action such as quitting smoking to reduce their child’s risk of respiratory complications. In addition, understanding the associations between different allergic conditions is a valuable first step toward recognizing the importance of comprehensive, multidisciplinary care of their child. General pediatricians who work with specialists such as allergists and dermatologists can be better prepared to address children’s needs in a coordinated way.

“Ultimately, this research is going to help inform clinical practice, for general pediatricians, and also allergists and pulmonologists,” Dr. Hill said. “It really is very hypothesis-generating for more basic science studies that can go forward to better understand what can be done to avoid the risk of asthma in what we may now perceive to be a higher-risk population of kids with other allergies.”