Since the beginning of the global pandemic, researchers have been racing to find out who is most at risk for SARS-CoV-2 and why.
Now a new population-based study by the National Institutes of Health (NIH) has found evidence of a curious benefit of the coronavirus for those with allergies.
In an analysis of more than 4,000 people, all living in households involving minors, the researchers noted several curious trends in SARS-CoV-2 infection, including that people with food allergies were only about half as likely to become infected.
The results are consistent with other recent studies that found that allergic conditions, such as asthma, may offer some protection against severe cases of COVID-19.
Somewhat similarly, the new NIH study found that asthma was not associated with an increased risk of SARS-CoV-2 infection, although asthma is a condition that affects the respiratory system.
On the other hand, obesity and high BMI are factors that increase the risk of SARS-CoV-2 infection, as well as the age of children and adolescents who share living space.
But the discovery of food allergies may be the most remarkable discovery.
“[T]he observed a link between food allergy and the risk of SARS-CoV-2 infection, as well as the body mass index, and this risk deserves further study, “said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.
Researchers aren’t sure why food allergies seem to make people less vulnerable to SARS-CoV-2, but there are several possible explanations.
Half of all study participants said they had been diagnosed with a food allergy, asthma, eczema or allergic rhinitis. These self-reports were then supported by a subset of blood tests that revealed antibodies associated with allergic disease.
Researchers then tracked the spread of SARS-CoV-2 in participating households from May 2020 to February 2021.
People with eczema and asthma showed no additional vulnerability to the virus, but also did not appear to be more protected.
Meanwhile, those with food allergies have a 50 percent lower risk of SARS-CoV-2 infection.
Not all forms of asthma are atopic (also known as severe allergies), and previous studies have shown that only those with atopic asthma express lower levels of the ACE2 receptor in the airway to which SARS-CoV-2 binds.
This suggests that the virus does not have as many ways to invade the cells in the lungs of those with respiratory allergies.
Something similar can happen in people with food allergies, although the authors only looked at SARS-CoV-2 infection, not the severity of the infection.
“It is not known whether this is the case for individuals with food allergies, but it is tempting to speculate that the type 2 inflammation characteristic of food allergies may reduce airway ACE2 levels and thus the risk of infection.” the researchers write.
“Supporting this possibility, we found significantly higher levels of general atopy among those with a food allergy self-assessment than those without a food allergy and even those with asthma.”
Interestingly, while some studies suggest that allergic asthma protects against severe cases of COVID-19, the current study found that the condition did not prevent the initial contraction of the virus.
Moreover, when a participant with asthma or food allergies becomes infected with the new coronavirus, he or she is less likely to be asymptomatic.
Further research is needed to distinguish the mechanisms behind the new findings, but the authors hope that their research may suggest new ways to prevent COVID-19.
The study was published in Journal of Allergy and Clinical Immunology.