Food Allergy Testing: Types, Symptoms, and How to Get Tested
Written By: Jillian Foglesong Stabile, MD, FAAFP
Quick Facts About Food Allergy Testing
- Skin tests, blood tests, and oral food challenges are common ways to test for food allergies.[5]
- Food allergies can cause severe reactions like anaphylaxis, unlike food intolerances.[1]
- Testing through an online provider offers a convenient option for food allergy screening.
What Is a Food Allergy?
A food allergy is an immune system reaction that can vary in severity from mild rashes to life-threatening reactions.[1] Food allergies occur when your body makes antibodies in response to foods that you eat, touch, or inhale. The antibody that mediates food allergies is immunoglobulin E (IgE).[2] If you have IgE antibodies, when you are exposed to the allergen, your body produces a large immune response and releases chemicals such as histamine that can cause the symptoms associated with food allergies.[2] Other types of food allergies can increase certain types of white blood cells in your system. These are called eosinophils.
What Is the Difference Between a Food Allergy and a Food Sensitivity or Intolerance?
A food allergy activates the immune system rather than the digestive system. Food allergies are generally more severe than food intolerances. Food allergies cause symptoms ranging from rashes to anaphylaxis and can be life-threatening if untreated.[3] Food allergy reactions often occur much more quickly than food intolerance reactions. In some cases, the reaction happens immediately after exposure.
A food intolerance is a digestive system reaction that is often mediated by immunoglobulin G (IgG). The symptoms of a food intolerance can be bothersome and affect your quality of life, but these types of reactions are not life-threatening. The symptoms of food intolerance can be very similar to those of food allergy, but generally, shortness of breath, swelling, and itching are not involved. Food intolerance reactions are usually slower to develop than food allergy reactions.
What Are the Symptoms of a Food Allergy?
The symptoms of food allergies can vary in severity. Some of the common symptoms of food allergy include[1]:
- Tingling of the mouth
- Itching of the skin or mouth
- Hives or eczema
- Swelling of the body, face, or throat
- Wheezing, congestion, or difficulty breathing
- Dizziness
- Fainting
More severe food allergy reactions can be life-threatening. Anaphylaxis is one such life-threatening reaction. Symptoms of anaphylaxis include[1]:
- Tightening of the airways
- Swelling or a lump sensation in the throat
- Difficulty breathing
- A rapid drop in blood pressure that can cause shock
- Fast heart rate
- Dizziness, severe lightheadedness
- Loss of consciousness
Anaphylaxis is a true medical emergency. Many people who have a history of anaphylaxis carry epinephrine to inject at the onset of a reaction. Even if epinephrine helps relieve symptoms, you should still seek immediate medical treatment because it is possible for symptoms to recur.
Another type of food allergy is food protein-induced enterocolitis syndrome (FPIES). This is a severe reaction in the digestive tract that occurs between two and six hours after consuming the offending food. This type of reaction is more common in infants who are being introduced to these types of foods for the first time and may cause severe vomiting, dehydration, or bloody diarrhea. This condition is an emergency and needs immediate medical attention.[4]
Who Gets Food Allergies?
Food allergies are very common. They occur in almost 6% of adults and children in the United States.[4] Food allergies often occur in infants and children, but they can happen for the first time at any age. Many infants and children with food allergies will outgrow them as they get older.
Any food can potentially cause a food allergy, but the most common food allergies are the top 9[4]:
- Eggs
- Dairy
- Peanuts
- Tree Nuts
- Fish
- Shellfish
- Wheat
- Soy
- Sesame
These allergens are common enough that the FDA requires them to be listed on the ingredient statement for all foods that contain these ingredients or are processed in a facility that also processes them.
Types of Food Allergy Testing: Skin, Blood, and Oral Tests
Food allergies may be evaluated and tested in several ways. The most common forms of testing are skin testing, blood testing, and oral food challenges.[5] Allergy testing can bring false positives, so it’s important to correlate the test results with your symptoms. For example, if food allergy testing says that you are allergic to milk, but you have no symptoms when you consume milk, it’s likely that the test is a false positive. Alternatively, if you have symptoms associated with exposure to the food, but the test is negative, it’s possible that the food could be a false negative. This is one of the reasons that working with a healthcare provider, such as an allergist, can be so helpful for interpreting results.
Skin Testing for Food Allergies
Skin testing is generally performed in an allergist’s office, though some forms of testing may be available through a primary care provider or otolaryngologist (ENT). This type of test involves using tiny needles to introduce an allergen under the skin on the back of the arm.[6] After a period of time, the pinpricks are examined for signs of a wheal (small bump) at the site. This test measures a histamine response to the agent introduced.
Skin allergy testing may be less accurate if you are on certain medications, so your healthcare provider may recommend refraining from taking certain medications prior to testing. It’s important to follow their instructions to avoid a false-negative result.[7] The size of the wheal that develops with exposure to the allergen doesn’t necessarily correspond to how severe a reaction you may have if you ingest or are otherwise exposed to the food. Skin allergy testing has a high false positive rate, so it is best interpreted in coordination with a healthcare provider.
Blood Testing for Food Allergies
Blood testing is generally considered less sensitive than skin prick testing. This type of test evaluates the amount of IgE in the blood. There are many options for this type of testing.[5] Blood allergy testing can be performed in person in a lab. There are also companies that offer blood testing that you can order online and perform in the comfort of your own home.
Blood allergy testing includes total IgE levels and IgE levels for specific allergens. This type of testing can be done on people who may not be able to have a skin test due to a dermatologic condition or certain medications.[8]
Blood allergy testing can have false-positive results up to 50%-60% of the time, so it is important to interpret results with caution and to follow the advice of your healthcare provider.[9]
Oral Food Challenge for Food Allergy Diagnosis
Oral food challenge is another type of allergy testing. The double-blinded oral food challenge is considered the gold standard for food allergy testing.[5] This type of testing involves increasing doses of the potential food allergen and monitoring for food allergy symptoms. This type of testing can be difficult to find and can be expensive. In this type of testing, neither you nor the person administering the test knows whether the food you’re consuming has the allergen in it.
Single-blind food challenges are very similar to double-blind studies, but in this type of study, the person administering the test knows whether the sample contains the allergen, but you don’t know. A third type of food challenge is an open food challenge, where both you and the person administering the test are aware of whether you are receiving the allergen.[10]
How Do I Get Tested for Food Allergies?
Food allergies are a significant concern for many people, but how do you go about getting tested? You can talk to your healthcare provider or specialist about which testing option is best for you. Working with a healthcare provider can also help you interpret the testing results. Another option for food allergy testing is to order through an online lab provider. There are many options available, and some of these labs will have access to virtual visits with a qualified healthcare provider, which provides an additional level of support for reviewing the results.
Take Control of Your Symptoms With Everlywell
Food allergies can cause significant distress and can also be life-threatening. You should seek medical attention if you’re experiencing severe symptoms. If you’re concerned or curious about food sensitivities, Everlywell offers an at-home Food Sensitivity Test that measures your body’s immune response to 96 common foods to help guide your food selection in a two-part elimination diet. If you have questions about your health, you can also schedule an online visit with one of our certified healthcare professionals.
References
- Mayo Clinic. Food allergy: symptoms and causes. Updated August 30, 2024. Accessed November 7, 2024. Medical Citation URL.
- National Institute of Allergy and Infectious Diseases. Causes and prevention of food allergy. Last reviewed June 10, 2024. Accessed November 7, 2024. Medical Citation URL.
- American Academy of Allergy Asthma & Immunology. Food intolerance defined. Updated July 8, 2024. Accessed November 7, 2024. Medical Citation URL.
- American College of Allergy, Asthma & Immunology. Food allergy. Last reviewed June 28, 2023. Accessed November 7, 2024. Medical Citation URL.
- Onyimba F, Crowe SE, Johnson S, Leung J. Food allergies and intolerances: a clinical approach to the diagnosis and management of adverse reactions to food. Clin Gastroenterol Hepatol. 2021;19(11):2230-2240.e1. doi:10.1016/j.cgh.2021.01.025
- American College of Allergy, Asthma & Immunology. Food allergy testing and diagnosis. Accessed November 7, 2024. Medical Citation URL.
- Mayo Clinic. Allergy skin tests. Updated March 26, 2024. Accessed November 7, 2024. Medical Citation URL.
- Cleveland Clinic. Allergy blood test. Last reviewed February 7, 2022. Accessed November 7, 2024. Medical Citation URL.
- Food Allergy Research and Education. Blood tests. Accessed November 7, 2024. Medical Citation URL.
- Food Allergy Research and Education. Oral food challenge. Accessed November 7, 2024. Medical Citation URL.