The study team monitored the infection by coronavirus in more than 4,000 people. This surveillance took place in 12 US cities between May 2020 and February 2021, before the widespread rollout of vaccines against the disease.
Participants were recruited from existing studies focusing on allergic disease. About half of participating children, adolescents and adults had a self-report of food allergy, asthma, eczema or allergic rhinitis.
When the study began, preliminary evidence from other research suggested that having an allergic disease may reduce a person’s susceptibility to SARS-CoV-2 infection.
Investigators found that self-reported, doctor-diagnosed food allergy halved the risk of infection, but asthma and the other monitored allergic conditions – eczema and allergic rhinitis – were not. associated with a reduced risk of infection.
The study authors believe that type 2 inflammation, a hallmark of allergic conditions, may reduce levels of an airway receptor protein used by the coronavirus to enter cells. Therefore, it would have a limited ability to infect them.
Differences in risky behaviors among people with food allergies, such as eating out less often, may also explain the lower risk of infection for this group.
However, through bi-weekly assessments, the study team found that households with food-allergic participants had only slightly lower levels of exposure than other households.