Medscape Medical News
New-Onset Allergies Another Woe for Patients With Long COVID
Lois Anzelowitz Levine, MA
January 27, 2026
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Summarize This Article
If your patients have been coming in with new asthma-like symptoms or sudden allergies to foods or the environment, long COVID could be to blame.
In an article published in Nature Immunology last December, researchers examined immunologic and inflammatory profiles in people with long COVID, comparing blood samples from patients who fully recovered from acute SARS-CoV-2 infection with those who developed prolonged symptoms. Their findings suggested long COVID is associated with persistent immune dysregulation, characterized by chronic inflammation, immune exhaustion, and disrupted energy metabolism. All of those could be contributing to the development of allergic reactions.
"While we have not examined allergies in our long COVID cohorts, it is plausible that SARS-CoV-2 infection could contribute to increased allergic responses," said Malika Boudries, PhD, an assistant professor of medicine at Harvard School of Medicine in Boston and first author of the study. "This hypothesis is supported by emerging evidence linking COVID-19 to immune dysregulation, including autoimmune phenomena and the reactivation of latent viruses such as Epstein-Barr virus," she said.
Another study published in the Journal of Allergy and Clinical Immunology evaluated the risk for new-onset type 2 inflammatory diseases after SARS-CoV-2 infection, using US electronic health record data from more than 118 million patients. After propensity score matching, investigators assessed new diagnoses of asthma, allergic rhinitis, chronic rhinosinusitis, atopic dermatitis, and eosinophilic esophagitis over a 3-month follow-up.
Following SARS-CoV-2 infection, participants were 74% more likely to be diagnosed with chronic rhinosinusitis, 66% more likely to be diagnosed with asthma, and 37% more likely to be allergic rhinitis.
By contrast, individuals who were vaccinated but not infected had significantly lower risks for asthma and chronic rhinosinusitis, and slightly lower risk of developing allergic rhinitis. "COVID-19 infection is associated with a heightened risk of respiratory type 2 inflammatory diseases, whereas vaccination appears protective," the researchers reported.
In a study to evaluate the relationship between SARS-CoV-2 infection and incident allergic disease, published in April 2024 in Nature Communications, investigators analyzed data from more than 22 million participants across South Korea, Japan, and the United Kingdom. The study excluded individuals with preexisting allergic conditions, such as eczema and food allergy and counted only new diagnoses occurring at least 30 days after SARS-CoV-2 infection.
The overall risk for allergy was approximately 20% higher in people who had COVID than in those who never developed the disease.
New-onset asthma emerged as the most consistent outcome, with more than double the risk observed in the Korean cohort. Allergic rhinitis incidence also increased, with a 23% higher risk after SARS-CoV-2 infection.
Ziyad Al-Aly, MD, is chief of research and development at the VA St Louis Health Care System in St. Louis and has been involved in over a dozen cohort studies defining postacute sequelae of COVID. He said mast cell activation syndrome (MCAS), which could present as allergies, is inherent to long COVID. Some allergy-like symptoms seen in long COVID may reflect MCAS, suggesting that mast cell dysfunction is "a key component of the condition," rather than a separate comorbidity, he said.
What Patients Are Saying, and Centers Are Seeing
Anecdotal evidence also bears out these links. On the social media site Reddit, threads dedicated to COVID and long COVID contain numerous stories of patients who developed new allergies, or whose existing allergies worsened, after developing the disease.
As one wrote: "I had only one allergy to milk. After COVID became allergic to legumes, brassica, dust, dander, hair, most laundry detergents, and all scented soaps."
Another stated: "I have acquired new allergies after every COVID infection. Beauty products, food, medication...crazy. COVID can activate mast cells which in turn release histamine = inflammation. If you look at the rise in autoimmune diseases post COVID, it's not much of a surprise. Our immune systems get ROCKED by this virus."
photo of Lisa Sanders, MD
Lisa Sanders, MD
Long COVID centers across the US are also seeing patients with allergic conditions presenting in myriad ways. Jacqueline H. Becker, PhD, is an assistant professor of medicine at the Icahn School of Medicine at Mount Sinai and a researcher with RECOVER-Neuro. "Long COVID is, at its core, a condition of immune dysfunction," Becker said. "New allergies are one manifestation of that dysfunction."
Lisa Sanders, MD, medical director for the Yale Long COVID program in New Haven, Connecticut, said she also suspects alterations in the immune system post-COVID are creating new allergic events — or reverting to past ones. Sander said she has noticed dormant allergies coming back to life after a SARS-CoV-2 infection.
photo of David Putrino, MD
David Putrino, PhD
"I have seen many new cases of asthma, or patients who had asthma as a child which had been quiet for many years and came roaring back after their COVID infection," she said. "Science is still trying to understand exactly what COVID-19 does to the body to trigger these long-lasting symptoms."
Some centers are reporting in food and chemical reactions as well. David Putrino, PhD, director of rehabilitation innovation at the Mount Sinai Health System in New York City, said he has observed sensitivities in many patients with long COVID. The list includes gluten, high-histamine foods such as nightshade vegetables and fermented foods, as well as sensitivities to a lot of scent-containing chemicals, such as perfumes, air fresheners, and detergents, he said.
photo of Monica Verduzco-Gutierrez, MD
Monica Verduzco-Gutierrez, MD
Monica Verduzco-Gutierrez, MD, chair of the Department of Rehabilitation Medicine at the Long School of Medicine at UT Health San Antonio, which operates a long COVID clinic, said her patients there exhibit a wide variety of allergic states. "We have seen asthma, allergic rhinitis, hives/urticaria, environmental and food allergies, with the most common being asthma. But then there is also a good subset of patients developing mast cell activation symptoms," she said.
She attributes these conditions to immune dysregulation. "That includes a tilt toward type-2 inflammation, altered B- and T-cell homeostasis, and even autoantibody formation. These call all manifest as new allergic disease," she said.
Besides vaccination, for prevention and the reduction of severe symptoms of COVID, some groups are looking at other early interventions that might reduce the immune changes associated with the disease.
photo of Fernando Carnavali, MD
Fernando Carnavali, MD
"Early screening for new or worsening allergies could capture and potentially modify the course of atopic conditions," said Fernando Carnavali, MD, the medical director of the Center for Post-COVID Care at Mount Sinai, in New York City. "We still need to determine whether the use of antihistamines or mast cell stabilizers in certain patients during the acute phase of COVID-19 could prevent the immunologic changes that lead to permanent allergies."
Identifying biological biomarkers early in recovery could help researchers find patients whose immune systems are going into an "allergic territory," especially those with a genetic predisposition to atopy, Carnavali added.
"Prospective studies are needed to follow patients from the moment of infection. Measuring specific biomarkers at baseline and throughout recovery would help prove that new-onset asthma is biologically 'allergic'", he said. "Treatment trials are certainly needed and should focus on high-risk groups, such as those with a family history of allergies or atopy."
"The reality is that there are at least 20 million Americans suffering from long COVID, and practitioners are bound to see these patients in their clinics," Al-Aly said. "Medical school curricula, graduate medical education, and continuing medical education programs should also incorporate the knowledge gained from this pandemic about long COVID and its myriad manifestations, including allergies and MCAS."
The sources in this story reported no relevant financial conflicts of interest.