On This Page:

What causes food allergies?
Why are food allergies a concern with GE foods?
How are GE foods tested for allergenicity?
Could genetic engineering reduce food allergies?
In a nutshell

Many common foods are known to cause allergic reactions in humans (see table below). The prevalence of food allergies in the U.S. is estimated to be between 1-3% of the adult population, with a slightly higher prevalence in children. The hypersensitive allergic response is triggered when a blood component called immunoglobin E (IgE) recognizes a specific protein (the allergen) in the food-- although not all proteins are allergens, all known allergens are proteins. The allergic reaction can cause symptoms that range from as mild as a skin rash or oral itching to quickly-fatal anaphylactic shock. Because of the potential severity of allergic reactions, the allergenicity of new food products should be considered carefully.

A novel genetically engineered (GE) food may have the potential to cause new allergic reactions if it contains proteins that the conventional food doesn't have. Of particular concern are GE foods engineered to contain a protein from a food already known to cause allergic reactions. If the protein in the GE food happens to have been an allergen in the original allergenic food, then it is possible that the GE food will also cause allergies. For example, people who are allergic to Brazil nuts may also be allergic to a GE soybean containing a Brazil nut protein.

In addition, that a protein is non-allergenic in one organism does not necessarily mean the protein will still be non-allergenic in the new GE organism. If a bacterial protein is moved into a plant, the plant may make alterations to the protein that bacteria don't make (called "post-translational modifications") which could affect its allergy-causing potential. At least one common plant protein alteration-- glycosylation, the adornment of a protein with long sugar-based chains-- has been demonstrated to have a large affect on the allergenicity of a protein. Furthermore, the quantity of protein produced may have an affect on allergenicity (although most transgenic proteins in GE plants are produced at very low levels relative to common allergens). On the other hand, some GE plants do not make a new protein at all (for example, Flavr-Savr tomatoes); they pose no new allergy risk.
[top of page]

Since 1992, the U.S. Food and Drug Administration has recommended (but not required) the developers of genetically engineered foods to assess their potential allergenicity, particularly if the food contains a protein from another food known to be allergenic. Although this assessment is not a legal requirement, so far all developers have submitted their products to the recommended allergy assessment. The FDA suggests that if there is insufficient evidence of a lack of allergenicity, the new product must be labeled or kept off the market entirely. In one case, however, a variety of transgenic corn which did not pass these allergy tests ("Starlink") was allowed to be marketed for animal feed. Here are the tests that are conducted:

•If the transgenic protein is from a common allergenic food.

The protein is isolated from the transgenic plant and first tested against the blood sera of allergic patients using standard allergy assays. If the tests demonstrate no sign of allergic response (or are unclear), the next step is a "skin-prick" test, in which allergic patients have a small amount of the protein injected under (or scratched into) their skin. If there is still no allergic response, a final food-consumption test (called the "double-blind placebo controlled food challenge") is conducted. If all of these tests cause no allergic response in patients normally allergic to the food the protein was taken from, the GE food is not likely to cause a cross-reaction allergy. This method of testing identified an allergen in one variety of transgenic soybeans, and prevented it from being marketed (see Case Study).

•If the transgenic protein is from a rare allergenic food.

If blood sera are available from allergic patients, tests are conducted as above. However, blood samples of patients with extremely rare food allergies (or even test patients themselves) may not be available. In this case, the food is tested as if the protein is from a source of unknown allergenicity (next section).

•If the transgenic protein is from an organism of unknown allergenicity.

Predicting the allergenicity of a food when there are no known allergic patients is extremely difficult. There is no reliable animal-testing method available to evaluate potential food allergens in either GE or conventional foods. Before a Brazil nut protein was genetically engineered into soybean, animal testing had suggested the protein would not cause allergies in humans. However, most known allergens do have some chemical properties in common, including relatively small size, and resistance to heat, acid, and stomach-enzyme degredation-- all characters thought to help the allergen get into the human blood stream intact. Although not all proteins with these characteristics are allergens, if a new protein from a GE plant shows any of these traits or has any other structural "sequence" similarities to a known allergen, the FDA considers the new protein to be a potential allergen and regulates accordingly.
[top of page]

Genetic engineering may actually have some potential to create "hypoallergenic" foods. Researchers in Japan have developed an experimental variety of GE rice that produces lower levels of rice allergens. Although the GE variety did have dramatically reduced levels of the allergens, it is not yet known whether this reduction in allergenicity is sufficient to allow normally rice-allergic persons to consume safely the new "hypoallergenic" rice as a part of their daily diets.
[top of page]

Some genetically engineered foods could have the potential to cause new allergic reactions if they produce a protein not normally present in the conventional food. This is particularly true if the GE food contains a protein taken from another food known to be allergenic (although there are none like this presently on the market). On the other hand, some GE plants do not produce a new protein at all, and therefore pose no new allergy risk.

Because of concern for allergenicity, the FDA suggests that all new GE products undergo some form of allergy testing before marketing. Although the testing is not mandatory, all GE foods presently on the market have undergone the available allergy tests.

Many experts feel that the likelihood of GE-induced allergies is very small, but agree that it is difficult, if not impossible, to predict the allergenicity of proteins in any new food (including new conventional foods) using current technologies. Proponents of GE-labeling argue that a lack of labeling prevents consumers from identifying and avoiding an allergenic food if an allergy develops, however rare.

Finally, genetic engineering may have the potential someday to reduce the allergenicity of commonly allergenic foods.
[top of page]

FDA. 1992. Statement of policy: Foods derived from new plant varieties; Notice. Federal Register. 57:22984-23005.

Franck-Oberaspach, S.L. & Keller, B. 1997. Consequences of classical and biotechnological resistance breeding for food toxicology and allergenicity. Plant Breeding 116:1-17.

Fuchs, R. & Astwood, J. 1996. Allergenicity assessment of food derived from genetically modified plants. Food Tech. 50 (2): 83-88.

Gall, H., Kalveram, K.J., Forck, G., Sterry, W. 1994. Kiwi fruit allergy: a new birch pollen-associated food allergy. Allergy Clin. Immunol. 94:70-76.

Gendel, S.M. 1998. Assessing the potential allergenicity of new food proteins. Food Biotechnology 12(3): 175-185.

Gendel, S.M. 1998. Sequence database for assessing the potential allergenicity of proteins used in transgenic foods. Adv. Food Nutr Res 42: 63-92.

Mendieta, N.L.R., Nagy, A.M., Lints, F.A. 1997. The potential allergenicity of novel foods. J. Sci Food Agric. 75: 405-411.

Metcalf, D., Astwood, J., Townsend, R., Sampson, H., Taylor, S., Fuchs, R. 1996. Assessment of the allergenic potential of foods derived from genetically engineered crop plants. Crit Rev Food Sci Nutr. 36(S):S165-S186.

Nakamuro, R., Matsuda, T. 1996. Rice allergenic protein and molecular-genetic approach for hypoallergenic rice. Biosci, Biotech, Biochem 60 (8):1215-1221.

Nordlee, J.S., Taylor, S., Townsend, J., Thomas, L., Bush, R. 1996. Identification of a brazil-nut allergen in transgenic soybeans. New England J.Med. 334:688-692.

Sanchez-Monge, R.L., Gomez, L., Barber, D., Lopez-Otin, A., Armentia, A., Salcedo, G. 1992. Wheat and barley allergens associated with baker's asthma. Glycosylated subunits of the alpha-amylase-inhibitor family have enhanced IgE-binding capacity. Biochem. J. 281:401-405.

Taylor, S.L. 1994. Evaluation of the allergenicity of foods developed through biotechnology. In: Proc 3rd Int Symp. Biosafety Results of Field Tests of Genetically Modified Plants and Microorganisms. University of California, Nov. 1994, pp185-198.