Food allergy testing explained

In 1912, Oscar Menderson Schloss became the first doctor to describe a food allergy test with skin prick testing. He noticed his patient had a bad reaction to eggs when he exposed the patient’s skin to egg whites. Over 100 years later, skin prick tests are still used today, representing a mainstay for diagnosing allergies.

Researchers have also uncovered a few more methods over the years, which is good news for the almost 6 percent of children and adults in the United States suffering from food allergies. Stick around to learn more about food allergy testing and who might benefit.

In this article:

What is food allergy testing?

Food allergy testing refers to different methods used to determine what foods someone is allergic to. The process can reveal what foods (or substances in foods) the body might mistake for something harmful entering its system. When this kind of reaction takes place, a variety of symptoms can show up, including stomach cramps, hives, itching, difficulty breathing, lip swelling, nausea, vomiting, diarrhea and life-threatening anaphylaxis.

Who might need a food allergy test?

Food allergies can sometimes run in families. People with eczema and asthma are also more likely to develop a food allergy. Individuals who experience symptoms suggestive of a true allergic reaction to a food should be tested for a food allergy. Additionally, experts recommend that food allergy testing should be considered for some young children with atopic dermatitis (eczema). The testing of siblings or other family members of children with food allergies is not currently recommended.

Food allergies: the “Big 9”

Researchers have documented allergic reactions to over 170 foods, but the vast majority of allergies stem from just 9 of them. They’re called the “Big 9,” and they include: eggs, fish, milk, peanuts, sesame, shellfish, soybeans, tree nuts and wheat.

Allergies to these specific foods are so common that the Food and Drug Administration (FDA) now requires food manufacturers to identify these ingredients on all labels.

Food allergy symptoms

Food allergy symptoms can vary. Some are hard to detect, while others demand emergency medical attention. Symptoms can include the following:

• Coughing
• Stomach cramping
• Diarrhea
• Dizziness
• Fainting
• Hives
• Eczema
• Runny nose
• Sneezing
• Wheezing or trouble breathing

The most severe reactions result in anaphylaxis, a life-threatening condition that causes the body to go into shock and impacts the ability to breathe. Anaphylaxis may also cause swelling around the face, neck, tongue or lips and a change in responsiveness.

What types of food allergy tests are there?

Today’s testing alternatives are more advanced than they were 100 years ago, even though the principles of the skin prick test remain the same. Listed below are the most common techniques health care providers use to diagnose food allergies.

These tests are good indicators of a food allergy, but a positive test does not guarantee that a patient will experience a bad reaction to that food. “False positives” typically occur for one of two reasons:

• The test detects proteins that are found in the same family of foods as the foods being tested but don’t cause a reaction.
• The test measures the body’s response to undigested food proteins, which are easier for the immune system to recognize and target.

A negative test is actually a much more useful way of ruling out potential food allergies.

Skin prick tests

Similar to Schloss’s method, this test requires practitioners to administer a drop of liquid containing a tiny amount of a potential food allergen. The skin is then pricked using a small, sterile probe, which allows the allergen to get under the skin. These allergens will remain there for about 20 minutes until test results are read. Tests are typically considered positive if a certain amount of swelling develops at the site.

Allergy blood tests

When a health care provider conducts an allergy blood test, they look for the presence of food-related immunoglobulin E (IgE) antibodies, which are produced by the immune system and in response to certain foods. The idea is that when these antibodies start to pile up, an allergic reaction is likely to occur.

In recent years, however, the accuracy of IgE tests has come under considerable scrutiny by organizations such as the American Academy of Allergy, Asthma & Immunology (AAAAI).

Although getting a blood draw is easy and convenient, a blood test can take several days to be sent out to the lab and reviewed by an expert. In comparison, the results of skin prick testing can be completed in under an hour.

Oral food challenge (OFC)

OFCs or feeding tests are another popular way to rule out food allergies, though they should only be performed under medical supervision. The process involves feeding patients trigger foods in a monitored health care setting, starting with small portions but gradually increasing the amount based on their response. (As soon as someone shows symptoms of a food allergy, the test stops.)

Experts have dubbed OFCs the most accurate food test available, and they remain a popular alternative for patients who have previously received inconclusive results with skin prick and blood tests.

Are food allergy tests covered by insurance?

Those affected by food allergies should contact their health insurance providers directly for information on their coverage and potential costs.

Key takeaways: food allergy testing

Food allergy testing can be a valuable tool for identifying triggers and improving overall well-being. Considering just how prevalent food allergies are, it can be beneficial to get familiar with appropriate testing strategies. People who suspect they may have a food allergy can always talk to a health care professional about available testing options and for additional guidance.