Family enjoys food at table.

What to Know Before Getting Tested for a Food Allergy

April 18, 2023

Food allergies can be complicated, and with more than 250 million people afflicted globally, it’s important to have a basic understanding of what they are and how to test for them. Here’s what you need to know: 


What are food allergies?

Some people’s immune systems are wired to identify normally harmless substances like pollen or pet dander as “invaders.” Their bodies react by releasing chemicals called histamines, which cause an allergic reaction. The same type of reaction can also occur with certain foods.

Sometimes called “The Big Nine,” the most common food allergies are to peanuts, milk, eggs, soy, wheat, shrimp/shellfish, tree nuts, sesame and fish, but there are more than 170 foods that can cause allergic reactions. When someone is exposed to a food they’re allergic to, they can experience a combination of symptoms, including:

  • Stomach pains
  • Diarrhea
  • Nausea/vomiting
  • Intense itching
  • Anaphylaxis (a severe, potentially life-threatening reaction)
  • Swelling of the face  
  • Rashes/hives

Despite how TV and movies sometimes depict allergic reactions, not all food allergies result in anaphylaxis. But since foods are the most common cause of anaphylaxis, it’s important to be prepared for the worst-case scenario if you have a food allergy.

The best way to avoid all food allergy reactions, whether mild or severe, is to talk to a healthcare provider, get allergy tested, and avoid your high-risk foods.

What’s the difference between food allergy and food intolerance?

A true allergy is caused by the immune system producing a particular type of antibody known as IgE, which helps destroy substances that the immune system believes to be dangerous and releases histamines in the process. From seasonal allergies  to food allergies, IgE antibodies are involved in most allergic reactions.

Having a food allergy can be extremely dangerous because it involves the whole immune system. Even inhaling microscopic amounts of certain foods could be enough to trigger an allergic reaction in people with food allergies.

On the other hand, food intolerance doesn’t involve the production of antibodies, and while having a food intolerance to lactose or gluten might cause digestive issues, the symptoms aren’t typically severe or life threatening. However, they can be very uncomfortable or painful. This discomfort can inhibit normal activities.

How do we test for food allergies?

There are two ways to test for food allergies. One way is to get a skin-prick test (SPT), where a provider pricks the top layer of your skin and inserts a small amount of the allergen in question. If you’re allergic to the substance, an itchy bump similar to a mosquito bite will form, and the provider will use that information to diagnose your allergies. The other way is to have your blood drawn and analyzed for specific IgE antibodies. We call this an allergy blood test.  

The more IgE that’s detected for certain substances, the more at-risk you may be for an allergic reaction. For example, if you’re allergic to peanuts, your test results will likely indicate a high level of peanut-specific IgE antibodies.

In a standard food allergy blood test, often called a whole allergen blood test, the IgE for the entire food substance is measured. For some foods, a more detailed allergy blood test called a food component allergy test is available, but only if ordered by a healthcare provider. Component testing measures levels of IgE related to specific proteins within an allergen. Some people may be allergic to a less dangerous protein in a food, which means they might be able to consume it under certain conditions. Talk to your healthcare provider directly if you’re interested in food component allergy testing.


You Can Purchase a Food Allergy Blood Test

Fortunately, you don’t have to be a medical provider to get a food allergy blood test for whole allergens. Labcorp OnDemand® can provide clarity as to whether or not you have a food allergy—quickly and easily. Our food allergy blood test measures your immune response to some of the most common foods known to trigger an allergic reaction. This test, along with symptoms and history, will help give you a better understanding of your body's reaction to common foods and guide your future food choices. For more information or to buy a test, click here.