When the HEROS study began, preliminary evidence from other research suggested that having an allergic disease might reduce a person’s susceptibility to SARS-CoV-2 infection. The HEROS investigators found that having self-reported, physician-diagnosed food allergy cut the risk of infection in half, but asthma and the other allergic conditions monitored—eczema and allergic rhinitis—were not associated with reduced infection risk. However, the participants who reported having food allergy were allergic to three times as many allergens as the participants who did not report having food allergy.
Since all these conditions were self-reported, the HEROS study team analyzed the levels of immunoglobulin E (IgE)-specific antibodies, which play a key role in allergic disease, in blood collected from a subset of participants. A correspondence between self-reported food allergy and food allergen-specific IgE measurements supports the accuracy of self-reported food allergy among HEROS participants, according to the investigators.
Dr. Hartert and colleagues speculate that type 2 inflammation, a characteristic of allergic conditions, may reduce levels of a protein called the ACE2 receptor on the surface of airway cells. SARS-CoV-2 uses this receptor to enter cells, so its scarcity could limit the virus’s ability to infect them. Differences in risk behaviors among people with food allergy, such as eating out at restaurants less often, also could explain the lower infection risk for this group. However, through biweekly assessments, the study team found that households with food-allergic participants had only slightly lower levels of community exposure than other households.
Interesting, and I hope this correlation leads to treatment or prevention measures for the general population down the line. As an anecdote, I have a food allergy and to my knowledge have not contracted the virus.