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Food Allergies, Part 1: Overview and Definitions
Dec 12

Food Allergies, Part 1: Overview and Definitions

By Ellen Marie Alonso Street, LMP Dietetic Intern

Special dietary needs are quickly becoming more widely recognized and accepted, reflected by increasingly accommodating menu options, entire aisles reserved for gluten-free goods, and school policies that create safe environments for children with severe allergies.

11% of the U.S. adult population and 8% of children in the U.S. have a food allergy.1,2 Odds are, someone in your life has a food allergy. Learning more about what causes an allergic reaction, how it’s diagnosed, and the treatments available can be helpful information for those struggling to find a diagnosis or looking for ways to support the people in their life with food allergies.

This four-part series will discuss the basics of food allergies, allergy testing and highlight three specific lesser known food allergies; Eosinophilic Esophagitis (EOE), Food Protein-Induced Enterocolitis Syndrome (FPIES), and Oral Allergy Syndrome (OAS).

What foods causes allergic reactions?

Food allergies are not the same as food intolerances because they can cause serious, life-threatening reactions! If you’d like to learn more about differences between food allergies and food intolerances, this article from the UPMC Allergy Center lists the differences. There’s a range of intensity when it comes to allergic reactions, from mild, non-threatening responses to life-threatening reactions. The foods that cause these reactions vary for everyone. Some people can tolerate small amounts, and others cannot be in the same room as the food without having a severe reaction!

You may already be familiar with the top 8 allergen foods: peanuts, tree nuts, wheat, eggs, milk, fish, shellfish, and soy. In this four-part blog series, we’re going to cover rare food allergies that are a bit more complex than straightforward reactions to the top 8 allergens.

What causes a food allergy?

People have reactions to these foods because they contain proteins that the body mistakenly interprets as harmful, triggering an immune response that can range from mild (itchiness, some hives), to severe, resulting in breathing difficulty and anaphylaxis, a potentially fatal.3

Testing for Food Allergies

Food allergies can be diagnosed several different ways, although not all food allergies are easily tested or diagnosed. Also, these tests aren’t always reliable, meaning that they can result in false positives or false negatives, indicating that there isn’t an allergy when there really is, or that there is an allergy when there really isn’t.4

We’ll cover four types of food allergy tests conducted by physicians and allergists: skin prick tests, blood tests, food patch testing, and food challenges.

Skin prick tests use a small amount of the allergen, placed underneath the skin with a needle, to test if the body’s immune system will respond, indicating an allergy. For a positive test, the skin will react by turning red and swelling within about 15 minutes of the skin prick.4 Blood tests are conducted by drawing blood and examining the blood sample for the presence of immune proteins, which can help pinpoint the type of immune response.4 The third type of test, food patch testing, is less commonly used and typically only useful for examining delayed reactions (24-48 hours after exposure) in children. A small piece of the suspected trigger food is placed in a small chamber called a Finn chamber and taped to the person’s back where is stays for 48 hours and is then removed. Results are read the next day and if the skin that touched the food is red and inflamed, the test is positive.4 Finally, food challenges are used to identify specific trigger foods by feeding the individual a certain, suspected trigger food in a controlled setting and waiting for a reaction to occur.4

If you are concerned that you or your child may be struggling with a food allergy, please contact your primary care doctor or pediatrician for an allergy consult.

Check out these other resources for food allergies:

Food diary: helpful for tracking reactions and symptoms. All reactions are important to note because even mild symptoms can evolve over time into more serious problems.
If you are looking to connect with other individuals living with food allergies, check out the online search tool created by Food Allergy Research and Education (FARE), to locate virtual and in-person allergy support groups near you.


  1. Jackson KD, Howie LD, Akinbami LJ. Trends in allergic conditions among children: United States, 1997-3011. NCHS data brief, no 121. Hyattsville, MD: National Center for Health Statistics. 2013. Retrieved from http://www.cdc.gov/nchs/products/databriefs/db121.htm
  2. Gupta RS, Warren CM, Smith BM, et al. Prevalence and Severity of Food Allergies Among US Adults. JAMA Netw Open. 2019;2(1):e185630. doi:https://doi.org/10.1001/jamanetworkopen.2018.5630
  3. Food Allergy Research and Education – What is a Food Allergy? (n.d.). Retrieved December 12, 2019, from https://www.foodallergy.org/life-with-food-allergies/food-allergy-101/what-is-a-food-allergy
  4. Food Allergy Research and Education – Diagnosis and Testing. (n.d.). Retrieved December 12, 2019, from https://www.foodallergy.org/life-with-food-allergies/food-allergy-101/diagnosis-testing