The 411 on food allergy testing

​Author: Savannah Weeks 
 
According to the National Institute of Allergy and Infectious Disease (NIAID), “a food allergy is defined as an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food.” Prevalence of food allergies has increased significantly over the past decade and is an important health issue for millions of Americans. However, false or clinically irrelevant positive allergy tests for foods are common. Indiscriminate and non-evidence-based screenings often lead to unnecessary dietary restriction.

Specifically, tests such as allergen-specific IgG are not supported by evidence and should not be used to diagnose food allergies. Only serum IgE tests and double-blind, placebo-controlled food challenges can be used to diagnose food allergies. Many serum samples show positive IgG results for foods that cause no clinical symptoms in patients. There are no controlled studies demonstrating the diagnostic value of IgG testing in food allergy. IgG results indicate that someone has been repeatedly exposed to food components, recognized as foreign proteins by the immune system. This does not mean that the person is hypersensitive to the food component, but rather that there is immunological tolerance. It merely shows a normal physiological response of the immune system after exposure to food components.
 
Food allergies can be frightening and serious, but they are still rare. It’s estimated that >20% of the population is modifying their diet due to a perceived food allergy, but it is estimated that only 4% of adults have true food allergies. Unnecessary dietary restriction can lead to nutrient deficiencies, lower quality of life, and decreased enjoyment of food. If you suspect you might have a food allergy, talk to your doctor and avoid testing from any non-medical professional.

References

1. Collins, S. C. (2016). Practice Paper of the Academy of Nutrition and Dietetics: Role of the Registered Dietitian Nutritionist in the Diagnosis and Management of Food Allergies. Journal of the Academy of Nutrition and Dietetics, 116(10), 1621-1631. doi:10.1016/j.jand.2016.07.018
   
2. Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel. (2010). Journal of Allergy and Clinical Immunology, 126(6). doi:10.1016/j.jaci.2010.10.007