You may have seen headlines this week that say food allergy can lower your risk for COVID-19 infection. These reports come from a NIH study (nicknamed HEROS*) published in the Journal of Allergy and Clinical Immunology. The headlines seem like good news. But a deeper look at the research shows that the connection between food allergy and lower infection risk might not be so certain. Here’s what you need to know about this study and the results.

Food Allergy Does Not Protect People From COVID-19

The results of the HEROS study suggest a lower infection risk, but not complete protection, for people with food allergy. And researchers are still not sure why food allergy would lead to a lower risk of COVID-19 infection.

“It is always important to look at methodology, as many studies, such as this one, are only designed to find associations of various patient characteristics with outcomes,” shared Dr. David Stukus, member of AAFA’s Medical Scientific Council and Professor of Clinical Pediatrics at Nationwide Children’s Hospital and The Ohio State University College of Medicine. “While this study identified fewer COVID-19 infections in participants who self-reported a history of food allergy, that information does not mean food allergies somehow caused that protection. While these findings are interesting, understanding these limitations is very important.”

The results of this study should not stop people from taking protective measures against COVID-19, including getting the COVID-19 vaccine. Taking these measures can protect both children and vulnerable family members.

Is Allergic (Type 2) Inflammation to Blame?

When looking at the results, the researchers thought that allergic inflammation might explain the lower infection risk for people with food allergy. This type of inflammation is known as type 2 inflammation. The COVID-19 virus uses a protein called the ACE2 receptor to enter cells and infect a person. Type 2 inflammation may lower levels of the ACE2 receptor on the surface of airway cells and lower risk of infection. Type 2 inflammation is common in food allergy. But type 2 inflammation is common in other allergic conditions like asthma, eczema, and allergic rhinitis too. But the study did not find a lower risk for COVID-19 infection for people with asthma, eczema, or allergic rhinitis. Therefore, it is unlikely that type 2 inflammation is the reason for lower infection risk among people with food allergies.

How Does Body Weight and Obesity Factor In?

The study also found that obesity (and high body mass index − BMI) raises COVID-19 infection risk. But the study did not address obesity in the food allergy data. People on restricted diets due to food allergies may have lower BMI, and this is unrelated to the allergic disease itself.

Behavior Offers a Better Explanation Why People With Food Allergies May Have Lower Risk of COVID-19 Infection

Researchers collected data for this study at the start of the COVID-19 pandemic. A more likely reason why people with food allergies had lower infection rates early in the pandemic relates to behavior. For example, people with food allergies eat out at restaurants less often to avoid allergic reactions. This behavior can also limit exposure to the virus that causes COVID-19. People with food allergies may have been extra careful during this time, which would have lowered their risk for infection anyway. These results highlight the importance of taking protective measures against COVID-19.

The Timing of the Study Affected the Results

The timing of the study is important to note. Researchers collected the data before COVID-19 vaccines became widely available. Vaccines offer more protection and have been proven to lower COVID-19 infection risk. The study period was also before the start of major variants like Delta and Omicron. These variants were more contagious than the original COVID-19 strain. More research is needed to understand infection risk in current times.

About the HEROS Study

The HEROS study looked at COVID-19 infection among people with food allergy, asthma, eczema, and allergic rhinitis. The HEROS researchers concluded:

• Having self-reported, doctor-diagnosed food allergy cut COVID-19 infection risk in half
• Asthma, eczema, and allergic rhinitis did not reduce infection risk
• Asthma did not increase infection risk

The study also looked at the risk of COVID-19 infection in children. Children 12 years or younger were as likely to become infected as teenagers and adults. But 75% of children who got COVID-19 did not show any symptoms, compared to 59% of teenagers and 37% of adults.

Researchers collected data between May 2020 and February 2021. The study monitored for COVID-19 infection in more than 4,000 people in over 1,300 households. About half of the children, teenagers, and adults in the study had food allergy, asthma, eczema, or allergic rhinitis.

Along with self-reports, the HEROS study team also looked at the levels of immunoglobulin E (IgE) antibodies. These antibodies play a key role in allergic disease.

To measure COVID-19 infection, participants took nasal swab tests every two weeks. They also filled out weekly surveys. Researchers collected blood samples during the study to measure IgE levels.

Key Takeaways

• For the first year of the COVID-19 pandemic, people with food allergies had a lower risk for getting sick with COVID-19, but the reasons why may relate to behavior and not disease.
• We need more research to understand the connection between COVID-19 and allergic diseases.
• Keep following recommendations to reduce your chances of getting sick.
• Remember, headlines don’t tell the whole story.

More information about the HEROS study can be found here.

For more information on COVID-19, asthma, and allergies, visit AAFA’s COVID-19 Resource Center.

*HEROS: Human Epidemiology and Response to SARS-CoV-2 (HEROS) study

Medical Review: June 2022 by David Stukus, MD, and Mitchell Grayson, MD, FAAAAI, FACAAI