Could GMOs Be the Cause of an Allergic Reaction?

Recently we received a consumer question about whether GMOs could be responsible for an allergic reaction of rash and hives after eating a salad with fruits and veggies.

To answer this, we reached out to Denneal Jamison-McClung, Associate Director – Biotechnology program at University of California-Davis.

Dr. Jamison-McClung:

There are only a few GM crops found in the fruit and vegetable aisles of the supermarket – squash, papaya and sweet corn. All of the other fruits and vegetables are not “GMO.”

Given what we know about the specific modifications made to GM squash, papaya or sweet corn, it is extremely unlikely that these foods would cause an allergic reaction. Food allergens have common characteristics (specific amino acid sequence, protein size/shape, abundance in the food, etc.) and all GM crops are screened to make sure that their proteins do not share characteristics with known allergens (Goodman, 2008). Specific techniques to assess allergenic potential in new crops, both GM and conventional, include detailed bioinformatic comparisons, immunologic assays and protein analyses (Houston 2013, Picariello 2011).

In the case of GM squash and GM papaya, both were developed because of viral diseases that threatened the crops. This gets a bit sciencey, but bear with me. To address that viral disease, genes that encode viral RNAs were incorporated. When the plant makes these RNAs, it triggers a cellular defense response at the start of infection (RNA homology-dependent gene silencing) that is somewhat like the immune response a vaccinated person would have against a specific disease (Morroni 2008, Collinge, 2010). In any case, neither of these GM crops expresses a GM protein with allergenic properties.

Sweet corn is engineered to express Bt protein in order to resist insect herbivores. Bt protein is safe for human consumption and is widely used by organic farmers as a spray. Bt proteins are non-allergenic, with the protein breaking down in our stomach acid within ~30 seconds (Adel-Patient 2011, Fonseca 2012).

It does sound like this reader may have a food allergy. My suspicion is that a common food allergen, such as egg in the salad dressing, may have been the cause of the reaction. The eight most common food allergens are milk, eggs, peanuts, tree nuts, fish, shellfish, soy and wheat (Mayo Clinic). I became allergic to eggs in adulthood, which was a surprise, as they were a significant part of my diet growing up. Unfortunately for me, eggs are found in all mayonnaise-based salad dressings and many other processed foods, making them difficult to avoid. People experiencing food allergy reactions, such as hives and rash, should follow up with a physician to receive testing for a panel of common food allergens. It is not possible for a medical provider to visually inspect a rash and pinpoint a specific allergen that caused the reaction – immunological tests, such as an IgE serum test, must be performed.


  • Adel-Patient 2011 – Immunological and Metabolomic Impacts of Administration of Cry1Ab Protein and MON 810 Maize in Mouse
  • Collinge 2010 – Engineering Pathogen Resistance in Crop Plants: Current Trends and Future Prospects
  • Goodman 2008 – Allergenicity assessment of genetically modified crops – what makes sense?
  • Fonseca 2012 – Characterization of maize allergens – MON810 vs. its non-transgenic counterpart
  • Houston 2013 – Quantitation of Soybean Allergens Using Tandem Mass Spectrometry
  • Morroni 2008 – Twenty Years of Transgenic Plants Resistant to Cucumber mosaic virus
  • Picariello 2011 – The frontiers of mass spectrometry-based techniques in food allergenomics

Canola Bokeh” by Leigh Schilling is licensed under CC BY.