by Charles Xu
figures by Krissy Lyon

Summary: People are concerned about the potential of GMO food to cause allergies. However, the technology used for making GMO crops does not necessarily make us more vulnerable than conventional breeding. Comprehensive evaluation for market approval, food safety surveillance, and adequate labeling could minimize the health risks of food allergies. Moreover, further development of technology might even enable us to remove the common allergens in our food.

In the autumn of 2000, a California woman named Grace Booth went into anaphylactic shock after eating three corn tacos; after ruling out all other food allergies, she became suspicious about the corn in the tortillas. Earlier that year, the consumer group Genetically Engineered Food Alert found that some Taco Bell shells, along with other corn products, contain a pest-repelling protein called Cry9C[2]. Originally from common soil bacteria, Cry9C can specifically destroy insect intestine and was introduced into StarLink GMO corn to kill predatory caterpillars (see this article). The StarLink corn had only been approved for animal feeding, and was never intended for human consumption because of concerns that Cry9C would be difficult to digest and cause an allergic reaction. However, it still entered the human supply due to cross-pollination when the GMO corn was planted too close to unmodified crops, and the tortillas that Grace ate were soon recalled due to contamination from a GMO product (Figure 1).

Although the Food and Drug Administration (FDA) did not find a direct link between Cry9C and allergic reactions in the consumers who claimed to have ingested StarLink corn, this recall spurred public discussion about the health risks of GMO foods. As a result, the scientific community is often asked if GMO foods make us more vulnerable to allergens, and how we can mitigate these potential risks.


Figure 1. Contamination of non-GM corn with GM corn StarLink containing the Cry9C protein may have caused an allergic reaction in one Taco Bell customer. It was not possible to prove a direct link between the Cry protein and the allergic reaction, but many believe this protien to be the culprit. Importantly, although many people ate the contaminated tacos, they were not all affected. Like any allergy, only those allergic to the allergen present in the contaminating corn would have an adverse reaction.

Allergens in GMO vs. non-GMO foods

An “allergy” is a hypersensitive immune response that occurs when a person comes into contact with specific substances called allergens. Allergies can lead to red eyes, itchy rash, swelling, runny nose, and breathing difficulties. Allergies are very common, and food-specific allergies affect 240-550 million people in the world[3]. In the US, 1 in every 13 children has a food allergy[5], and the prevalence of childhood allergies has increased by more than 50% in the last 20 years[7]. A combination of host and environmental factors determine the intensity of allergic reactions: increased vulnerability can be attributed to various factors including changes in lifestyle, hygiene, diet, and physical activity. However, there is no evidence that GMOs are any more or less allergenic than their non-modified counterparts.

Ninety percent of food allergies are caused by the common allergens in peanuts, tree nuts, milk, eggs, wheat, soy, shellfish, and fish[9]. In 1996, researchers found that the main allergen from Brazil nuts retains its allergenicity after being transferred into a GMO soybean; the Brazil nut GMO soybean has never been approved for the market, and this case helped establish the policy that any protein that has been shown or even suspected to cause an allergic reaction should never be introduced into a GMO crops. According to the international principles of food safety (FAO/WHO), before any GMO food gets market approval, the structure of the introduced protein should be compared to all known allergens. Potential allergenicity is then further analyzed with comprehensive experiments. Additionally, as part of post-marketing monitoring, randomly sampled consumers are examined to detect previously unidentified allergenicity. Currently, around 30 GMO crops have received approval in the US, and most of our corn, soybeans, and cotton are GMO crops. To date, no allergens have been found in GMO products approved for human consumption.

Regulation of Allergens

Since GMO market approval is under strict regulation, we should probably be more concerned about contamination from unauthorized GMOs (such as StarLink corn) than about allergies to common GMO foods. GMO plants can spread their genes to conventional crops through cross-pollination. To avoid such occurrences, there are guidelines stipulating that GMO plants should be physically segregated from the closely related plants by a buffer zone that is sized proportionally to how far the pollen can travel; however, it must be considered that not all farmers will obey these guidelines, and some pollen can travel unexpectedly long distances via bees or other pollinators. With this in mind, the European Union (EU) scientific committee on plants states that contamination is unavoidable[6], and therefore, the consequences of contamination should be considered before market approval. However, if contamination occurs, it is possible to eliminate the food containing the suspicious or unexpected allergens via a robust safety surveillance system. In fact, the scrutiny for common allergens in our food supply has been in practice long before the emergence of GMO foods. After the recall of StarLink corn and the subsequent ending of its planting, the presence of Cry9C residues was monitored for many years until the corn supply was essentially free of StarLink[11].

As different individuals can be allergic to different foods, the major risk of food allergy comes from unwitting ingestion of the allergen. Therefore, it will be helpful for every consumer to know the exact composition of their food, where it is genetically modified or not. Mandatory labeling of GMO ingredients, which has been required by law in the EU but not the US, could help consumers identify the potential allergens and facilitate the recall process, if necessary. However, unless it involves common allergens such as gluten and peanuts, the labeling of even non-GMO food is often inadequate. Thus, there does not appear to be particular bias towards poor labeling in GMO foods only.

Figure 2. GMOs could be used to remove allergens from food, allowing those with allergies to eat food that they previously couldn’t. This technology is still in development, but it could be the future of staying allergen-free.

Removing Allergens by Genetic Engineering

With appropriate oversight, the technology used for engineering GMO crops need not cause more allergic responses than conventional breeding. On the contrary, we rely on GMO technology to overcome some of the most difficult challenges for food safety. For example, to prevent contamination, scientists are engineering GMO crops to only self-pollinate or fertilize with manual assistance[1,8]. Additionally, it has recently been reported that scientists can reduce or remove the common allergens in our crops with GMO technology (Figure 2). This was most strikingly demonstrated by an international team of researchers that suppressed the enzyme responsible for making gluten in wheat, leading to a resulting GMO wheat with a 76.4% reduction of gluten in its seeds[13]. Admittedly, there is still a long way to go before we could enjoy a roll of bread made from gluten-free GMO wheat, but such preliminary success has inspired us to believe in that future development of GMO technology could become a solution to, rather than a cause of, food allergies.

Charles Xu is a Ph.D. candidate in the Biological and Biomedical Sciences program at Harvard University

This article is part of the August 2015 Special Edition, Genetically Modified Organisms and Our Food.


1. Daniell H. (2002). Molecular strategies for gene containment in transgenic crops. Nature Biotechnol 20: 581-586
2. Pollak A. (2000). Kraft recalls taco shells with bioengineered corn. New York Times.
3. 2013 white book of the World Allergy Organization
4. Celec, P et al. (2005). Biological and biomedical aspects of genetically modified food. Biomed Pharmacother 59, 531-540.
5. Gupta RS et al. (2011). The prevalence, severity, and distribution of childhood food allergy in the United States. J Pediatr 128.doi: 10.1542
6. Haslberger A. (2001). GMO contamination of seeds. Nat Biotechnol 19, 613.
7. Jackson K et al. Trends in Allergic Conditions among Children: United States, 1997-2011. National Center for Health Statistics Data Brief. 2013. Retrieved from
8. Muhammad SK. (2005). Plant Biology: Engineered male sterility. Nature 436:783-785
9. NIAID-Sponsored Expert Panel. Guidelines for the diagnosis and management of food allergy in the United States: Report of the NIAID-sponsored expert panel. J Allergy ClinImmunol.2010; 126(6):S1-S58.
10. Nordlee, JA,et al. (1996). Identification of a Brazil-nut allergen in transgenic soybeans. N Engl J Med 334, 688-692.
11. Petersen B, et al. (2006) Revised StarLink corn risk assessment and updated QCP data through October 2006. EPA Memorandum WD00702.000 B0T0 1206 0001
12. Jeffrey Smith. Seeds of deception: exposing industry and government lies about the safety of the genetically engineered foods you’re eating. ISBN: 0-9729665-8-7
13. Wen S et al.(2012) Structural genes of wheat and barley 5-methylcytosine DNA glycosylases and their potential applications for human health. PNAS 109: 20543-20548

36 thoughts on “Nothing to Sneeze at: the Allergenicity of GMOs

  1. Woah, outsanding work charles, truly a succulent bite of information to please my tastes 😉

    I do believe me this has got to be one of the pages of all time, I for one especially loved the images in this article, just immaculate reasearch mate.

    If you’re interested in coming on my podcast “Pigs do fly”, please hit goody me up on a lickety split

    Thanks, Charles…

    1. Good evening Mr. Walter John Reggie IV,

      My name is not Charles but I can become him. It would be my greatest honor to go on your podcast, “Pigs Do Fly”. If you would like to extend your invitation to me, please do reach out. Thank you for the consideration, I humbly await your careful deliberation.

      Sincerely, Not Charles

    2. Good evening Sir Walter John Reggie IV,

      My name is Not Charles, but for you dear sir, I can become Charles. If it would be pleasing to you as to extend the offer of joining your podcast, “Pigs Do Fly”, I would be most delighted to join. So please, do hit me up a good ol’ lickety split. I humbly await your response.

      With love, Not Charles

  2. I just ate some GMO pinto beans and had a major allergic reaction including itchy eyes and skin, stuffed nose, rapid heart beat. I’m usually very careful about what I eat but this batch made it past my radar and I ate a bowl of them.

    The fact is there is not enough solid science backing up GMOs as safe for human consumption in the long term (or short term, really) corporations lobbied to have a legal margin of error included in the regulations so that they could sell their GMOs without having to really be accountable for their bad science….it’s a concept called “substantial equivalence” meaning “it’s close enough to be sellable”.

    The natural foods we have been eating for our species’ entire evolutionary existence also took millions of years to come into being and we co-evolved right along with them, our bodies being affected in ways we don’t clearly understand yet. So how could a lab that JUST created GMOs ever be able to forecast how and what kind of effect these foods will have on us?

    They can’t. The data set is too small and the time too short, but because it hasn’t killed the lab rats and cows, then “substantial equivalence”.

  3. I enjoyed reading every bit of this article, including the comment section.
    Thank you very much.
    Food allergy is one, but I’m surprised how little the media talks so little about nickel allergens. Almost everyone we know has some level reaction to nickel! I recently found out how the majority of products (food too) we consume and or interact with daily contain a shockingly high level of nickel in it.

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