How to know if you have a food allergy

Medically reviewed on June 14, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Table of contents

• Step 1: Observe symptoms
• Step 2: Allergy testing
• Step 3: Visit your healthcare provider
• How to live with a food allergy
• IgE food allergy testing at home
• Related content

Whether you have an egg allergy, wheat allergy, shellfish allergy, or peanut allergy, experiencing an adverse response to certain foods is far from uncommon.

The American College of Allergy, Asthma, & Immunology estimates that food allergies affect 1 in 10 American adults [1]. While most food allergies appear in childhood, affecting between 4–6% of young children, around 15% of food allergies crop up later in life [2, 3].

Observing adverse health effects in response to a food agent is usually the first sign of a food allergy, but more subtle cues from the body may call for a more comprehensive food allergy assessment.

If you suspect you may have a food allergy but aren’t sure how to confirm it, food allergy testing can be an important step toward identifying allergens. In this article, we’ve outlined the three-step process for knowing whether you have a food allergy, so read on.

Step 1: Observe symptoms

Do you get rashes after eating some peanuts? That's one of the most common peanut allergy symptoms. A common initial sign of a food allergy is experiencing physical changes following exposure to a certain type of food.

Food allergy symptoms exist on a continuum from mild to severe. Someone with an allergy to peaches, for instance, may experience a gentle swelling of the tongue and a mild itching at the back of the throat. However, people with a shellfish allergy—increasingly the most common and often serious food allergy—may experience acute symptoms, such as hives, vomiting, or even anaphylaxis, within minutes of ingesting a single oyster [4].

When taking note of any physical changes you may experience after exposure to certain foods, keep in mind that there’s a distinction between a food intolerance and a food allergy:

• Intolerance – Food intolerances can be uncomfortable or even debilitating, but they do not trigger an immune reaction. Most food intolerances arise due to the body’s inability to process certain food ingredients. This may be because the digestive system lacks a certain enzyme needed to digest a food (as in the case of lactose intolerance) or because a certain food item contains chemical preservatives [5].
• Allergy – A food allergy occurs when the immune system judges a certain ingested substance as a threat. This triggers a deluge of antibodies, chiefly immunoglobulin IgE, which causes the body to release histamines. Histamines are the molecules that tell the cells in the body to defend themselves against this perceived threat (be it a sesame seed or a piece of shrimp) [6].

Food allergy symptoms to look for

The body is a comprehensive organism, and each of its systems works in concert. For this reason, food allergy symptoms are likely to affect more than one system simultaneously.

There are typically four principal systems in play during a food-related allergic reaction [3]:

• Digestion – Given that the entry of food into the digestive system is typically what triggers an immune response, it may come as no surprise that many allergens lead to digestive or gastrointestinal distress. Stomach pains, cramping, and diarrhea are all common digestive symptoms that may be associated with a food allergy.
• Respiration – Wheezing, coughing, or a constriction of the breathing passages may all be a part of the food allergy response. Food allergies may also trigger tongue or esophageal swelling, which can inhibit airways and severely compromise normal respiration.
• Circulation – Food allergies can cause dizziness, low blood pressure, and fainting—all manifestations of depressed circulation. Milder symptoms may include a weak pulse or even a pale, wan skin tone.
• Skin – Cutaneous (skin) reactions to food allergens tend to vary widely in severity, from slight itchiness of the skin to body hives.

Anaphylaxis is a rare but serious and potentially fatal food allergy reaction, which may result in vomiting, a swelling of the skin and airways, loss of consciousness, or even cardiac arrest [7]. While anaphylaxis onset is typically acute, a biphasic anaphylactic reaction can occur up to 12 hours after the initial exposure to a food allergen [8].

Although life-threatening food allergies are rare, identifying them can help you understand your food triggers and reduce the risk of experiencing severe reactions.

Step 2: Allergy testing

The next step for confronting a suspected food allergy is to take a food allergy test.

IgE food allergy tests (like the Everlywell at-home Food Allergy Test) are not a diagnostic tool for food allergies. Rather, they offer a preliminary gauge of your IgE immune response to certain foods.

While everybody’s body contains IgE, people with food allergies have more active IgE antibodies than others. At-home food allergy tests are typically administered by taking a finger prick-sized blood sample and running it through a CLIA-certified laboratory.

The Everlywell Food Allergy Test tests 9 common food allergens, including:

• Dairy
• Eggs
• Fruits and vegetables
• Grains
• Legumes
• Meats and seafood
• Nuts and seeds
• Spices

If you want to discover which foods your body is reactive to, a food allergy test can be a reassuring first step in deciding whether to move forward with a diagnostic assessment.

Step 3: Visit your healthcare provider

For some, the allergy test is the end of the road: if their results demonstrate a strong immune response to a certain food, they eliminate it from their diet.

In some cases, however, you may want to graduate to the next stage of food allergy assessment: diagnostic testing.

Diagnostic food allergy testing may be necessary for people with serious food allergies. For instance, severe nut allergies can be particularly insidious given the prevalence of trace nuts in many common foods.

Because the process of food allergy testing can be a lengthy undertaking, it may be helpful to know what to expect before you book your first appointment. Food allergy testing usually involves four components [9]:

• Oral test – During an oral challenge test, you’ll ingest a small amount of a suspected food allergen either in pill form or through an injection. Oral tests are closely monitored to provide emergency care if necessary.
• Skin prick test – This type of test gauges the body’s reaction to superficial contact with a suspected food allergen. Skin pricks involve putting a small amount of an ingredient on the arm or back and lightly pricking the skin to admit a tiny sample beneath the skin. For people with food allergies, this may cause swelling, itching, or a rash.
• Labs or blood tests – Food allergy blood tests are a bit different from food sensitivity tests. They measure the reactivity of IgE immunoglobulins to certain food substances. These tests occur in a lab, so the body isn’t exposed to the allergen.
• Elimination diet – Aside from these slightly more invasive tests, an allergist may recommend eliminating suspected allergens from the diet to see if symptoms improve. After elimination, you’ll reintegrate suspected allergens one by one to see whether they trigger an adverse reaction. This can help you get a clearer picture of which specific foods the body may be allergic to.

How to live with a food allergy

Living with a food allergy often means making lifestyle adjustments to avert exposure to certain foods and ingredients. In addition, an allergist may recommend a treatment protocol to improve your overall quality of life.

Treatment plans for food allergies are highly contingent on the individual, their unique immune response, and the severity of their symptoms. To that end, treatment protocols tend to assume the following forms:

• Elimination – The most comprehensive intervention for a food allergy is to cut out foods that aggravate symptoms. In some cases, elimination also requires avoiding certain food products, as even indirect exposure can trigger some allergic reactions.
• Medication – Medications like antihistamines can work wonders for combating mild to moderate food allergies. Antihistamines work by limiting the number of histamines released during an allergic reaction, tempering immune responses that can result in itchiness, swelling, or hives [10]. For more severe food allergies, a healthcare provider may prescribe you an epinephrine injector or “EpiPen.” EpiPens are injected under the skin to control life-threatening symptoms that arise in the event of an anaphylactic emergency.
• Oral immunotherapy – Occasionally, an allergist may recommend a therapeutic protocol for reducing the reactivity to food allergens. Oral immunotherapy works by gradually introducing small amounts of food allergens to the immune system so that it learns to recognize them as non-threatening [11].

Although you may find it challenging to live with a food allergy, it can help to remember the bigger picture at hand: allergies are a sign that the body is doing its best to protect you from harm. By testing for food allergies, you can extend to your body the same care and protection.

IgE food allergy testing at home

With the Everlywell at-home Food Allergy Test, you can learn your IgE reactivity to common food allergens. If you receive test results indicating increased reactivity that may be connected with a food allergy, you will receive a call from a nurse to help with next steps.

Related content

Peanut allergy symptoms explained

Food allergy, food sensitivity, and celiac disease: An expert explains the key differences and how to test

Meet our first at-home Food Allergy and Celiac Disease Screening tests

References

1. Warren CM, Jiang J, Gupta RS. Epidemiology and Burden of Food Allergy. Curr Allergy Asthma Rep. 2020 Feb 14;20(2):6.

2. Food Allergy. American College of Allergy, Asthma, & Immunology. URL. Accessed June 14, 2022.

3. Facts and Statistics. Food Allergy Research & Education. URL. Accessed June 14, 2022.

4. Wai CYY, Leung NYH, Chu KH, Leung PSC, Leung ASY, Wong GWK, Leung TF. Overcoming Shellfish Allergy: How Far Have We Come? Int J Mol Sci. 2020 Mar 23;21(6):2234.

5. Ortolani C, Pastorello EA. Food allergies and food intolerances. Best Pract Res Clin Gastroenterol. 2006;20(3):467-83.

6. Histamine: The Stuff Allergies are Made of. National Institute of Health. URL. Accessed June 14, 2022.

7. Anaphylaxis. American College of Allergy, Asthma, & Immunology. URL. Accessed June 14, 2022.

8. Reber LL, Hernandez JD, Galli SJ. The pathophysiology of anaphylaxis. J Allergy Clin Immunol. 2017 Aug;140(2):335-348.

9. Food Allergy Testing. National Library of Medicine. URL. Accessed June 14, 2022.

10. Antihistamines. StatPearls [Internet]. URL. Accessed June 14, 2022.

11. Treatment for Living With Food Allergy. National Institute of Health. URL. Accessed June 14, 2022.