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A history of SARS-CoV-2infection significantly increased the risk of developing six allergic conditions, based on data from more than 760,000 adults and children.

The development of atopic conditions in the wake of viral illness has been well documented, and some research has described an associated between SARS-CoV-2 and an increased risk for various allergy-associated diseases in adults and children, wrote Jessica Clarion, MD, a pediatrician at the Uniformed Services University of the Health Sciences, Bethesda, Maryland, and colleagues.

SARS-CoV-2 has shown a tendency to disrupt immune function both acutely and in the recovery period, manifesting in conditions that include multisystem inflammatory syndrome in children , long COVID, and allergic diseases, Clarion said. However, studies of the COVID and allergic disease relationship are limited and have shown conflicting results.

In a new study published in the Annals of Allergy, Asthma & Immunology, the researchers assessed data from the TRICARE Management Activity’s Military Health System Data Repository, a US Department of Defense healthcare claims database, from July 2018 to December 2022 that included inpatient and outpatient medical records, COVID lab results, and dispensed prescriptions.

The full study population included 767,715 individuals aged 1-64 years. The median age was 31 years, and 44.89% were women. At baseline, 262,332 had a history of COVID and 522,664 served as control individuals; 16,281 control individuals were moved to the COVID group during the study period based on COVID diagnoses or lab tests.

The researchers estimated hazard ratios (HRs) for the entire cohort for the development of atopic dermatitis, asthma, food allergies, rhinoconjunctivitis, medication allergies, or urticaria over an 18-month follow-up period, and conducted sub-analyses in children and active-duty service members. The incident outcomes were assessed between 31 and 548 days after entry into the study.

Overall, SARS-CoV-2 infection was significantly associated with an increased risk for all six conditions, with HRs of 1.08 for atopic dermatitis (P = .0005), 1.09 for medication allergies (P < .0001), 1.10 for urticaria (P = .0001), 1.11 for food allergies (P = .0002), 1.25 for rhinoconjunctivitis (P < .0001), and 1.54 for asthma (P < .0001).

A subgroup of active-duty military personnel aged 17-64 years included 103,789 with COVID and 207,578 control individuals. In this group , only asthma and rhinoconjunctivitis risk increased significantly with a history of SARS-CoV-2 infection (HR, 1.55 and HR, 1.17, respectively; P < .0001 for both).

A pediatric subgroup included 32,118 children aged 1-17 years with COVID and 64,236 control individuals. In this subgroup, all conditions except for food allergies were more likely with a history of SARS-CoV-2 infection. HRs were 1.15 for atopic dermatitis (P = .0069), 1.20 for urticaria (P = .0018), 1.24 for medication allergies (P = .0012), 1.38 for rhinoconjunctivitis (P < .0001), and 1.82 for asthma (P < .0001 ).

The consistency of the findings for multiple allergic conditions across distinct age groups was particularly noteworthy as these data offer additional points of evidence toward the risk for allergic conditions after COVID exposure, Clarion said.

However, “Our findings do not establish that SARS-CoV-2 directly causes allergic disease, nor do they confirm allergic sensitization,” Clarion emphasized. “The primary takeaway for clinicians is that allergy-related diagnoses may be seen more frequently following COVID-19 infection, and that new symptoms consistent with the incident outcomes of interest may represent more than nonspecific post-viral complaints,” she said.

The findings were limited by several factors including the retrospective and observational design, as well as the lack of control for non-COVID viral exposures that could have contributed to the development of atopic conditions, and the inability to account for the effect of COVID vaccination.

“Additional studies that incorporate clinical and laboratory markers such as allergen sensitization testing, IgE levels, and pulmonary function testing will be valuable in distinguishing true allergic disease from other post-infectious conditions, as will mechanistic investigations that determine if SARS-CoV-2 specifically promotes type 2 inflammation,” Clarion said.

Pay Attention Post-COVID

The new study supports the need for clinicians to monitor patients for new allergic diseases for up to 18 months after a SARS-CoV-2 infection, said Arianne K. Baldomero, MD, MS, ATSF, a pulmonologist, critical care physician, and assistant professor of medicine at the University of Minnesota, Minneapolis.

Given that allergic symptoms such as cough, congestion, and rashes overlap with those of long COVID, it is essential to properly diagnose allergic symptoms as distinct atopic conditions to ensure prompt, targeted intervention, said Baldomero, who was not involved in the study. “Allergic diseases, including asthma, allergic rhinitis, and atopic dermatitis are highly prevalent in both adults and pediatric population; therefore, it is crucial to evaluate underlying biological mechanisms, such as postinfectious immune dysregulation,” she said.

The study findings were not unexpected, as a T helper2-skewed immune response is biologically plausible after viral infection, said Baldomero. “However, it is interesting that active-duty adults only saw a significant increase in asthma and rhinoconjunctivitis,” she noted.

Further research is needed to determine the exact duration of the postviral risk and whether it extends to other common viruses such as rhinovirus and influenza, Baldomero said. “Future studies should investigate clinical management strategies, including whether early interventions and which therapies can actively prevent the development of these allergic diseases,” she added.

The study was funded by an intramural award from the Uniformed Services University of the Health Sciences. The researchers had no financial conflicts to disclose. Baldomero had no financial conflicts to disclose.