Food Allergy Test: Signs, Symptoms, & Home Kits

By Charlie Huntington, M.A., Ph.D. Candidate
​Reviewed by Tchiki Davis, M.A., Ph.D.
Food allergies are becoming more common, so we need effective food allergy tests to keep us informed and safe. Let’s see how testing works, including at home.​
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When I was a first-year college student, I started studying Arabic. After a couple weeks had passed and our knowledge of Arabic had expanded far enough for us to be able to say things such as “please,” “thank you,” and “good,” our professor brought us our first course of traditional Middle Eastern snacks. I remember settling into my seat with a handful of desserts and then, perhaps fifteen minutes later, starting to feel a little funny.​
 I went to the bathroom—a word I thankfully knew in Arabic by this time!—but it was not a digestive issue. Instead, I was having my first allergic reaction to a food.

Over time, I came to recognize that the substance affecting me was tahini, the paste made from sesame seeds and used (unfortunately for me) in many Middle Eastern dishes and desserts. Since then, I have avoided tahini as much as possible; if I accidentally consume some, I feel some of the symptoms of an allergic reaction, but thankfully it is never a severe one.

Perhaps you have your own story like mine, and perhaps the experiences you had were enough to guide your decision making around food. But sometimes the answers are not very clear, and we need the help of something like a food allergy test to determine what is really affecting us.​
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What Is a Food Allergy Test? (A Definition)

First of all, what is a food allergy? A food allergy is an unpleasant or unhealthy effect that occurs when you eat a certain food and your immune system has an adverse reaction to it (Boyce et al., 2011). Food allergies are surprisingly common: It is possible that as many as 30% of all children have a food allergy, with some commonly eaten foods being those to which children are most likely to be allergic (Pyrhönen et al., 2011).
 
There are several kinds of food allergy tests. One that is considered the gold standard, perhaps because it is as close to real-life testing as possible, is called an oral food challenge (Sampson et al., 2012). This kind of test is usually conducted in a doctor’s office and consists of giving the patient gradually increasing amounts of a food to which they may be allergic. This is not something to be tried at home; the reason it happens in a doctor’s office is so that a medical provider with the ability to treat any kind of severe allergic reaction, such as anaphylaxis, is present and able to intervene immediately. This is considered a preferable approach because it is the most naturalistic of the food allergy tests and because a medical professional who can recognize signs and symptoms of an allergic reaction is able to witness them occurring (or not) in real time (Sampson et al., 2012).
 
A second type of food allergy test, which has been used often since the 1950s, is called skin prick testing (LaHood & Patil, 2019). In this method, a tiny amount of the food substance being investigated is applied to a person’s skin, and then the skin is pricked—not deep enough to draw blood but sufficiently so that the food substance can interact with the more vulnerable skin cells underneath the top layer. If the skin changes color and puffs up slightly, it indicates an allergic reaction.
 
The advantages of this method are that it can be performed easily with a variety of tools such as needles, and it puts the patient at lower risk of a severe allergic reaction (LaHood & Patil, 2019). This is also not something to try at home, as most doctors acquire the extracts of various foods from professional sources, use sanitized and sterile tools, and are familiar with how different reactions to the extracts will look—not things most people could be expected to comfortably pull off at home.
 
The most commonly used form of testing is a serum test, or blood test, in which cells from our blood are exposed to allergens and are observed to see whether they demonstrate an immune response (LaHood & Patil, 2019). While this does not prove that a person will have an allergic reaction to a real-life encounter with a certain food, it can strongly indicate whether their body has developed a strong immune response to certain foods.
 
A highly thorough approach to food allergy testing would potentially combine these methods to test as comprehensively as possible (LaHood & Patil, 2019). For example, if skin prick or serum testing reveals the possibility of allergies to specific foods, an oral food challenge may be used to confirm the food allergy.​

IgG vs. IgE Food Allergies​

Food allergies are sometimes classified as either Immunoglobulin E (IgE) or Immunoglobulin G (IgG) allergies (Collins & Jackson, 2013). IgE allergies are in line with what most of us imagine to be the standard allergic response: They begin to appear within minutes of eating the food and can be severe. IgE allergies develop because the immune system interprets a certain food substance as something toxic instead of something safe and nutritious to eat. It then develops antibodies that are ready to react to another exposure to the food by causing the symptoms we associate with allergic reactions, such as itching and inflammation. Other symptoms of IgE allergies can include hives or rashes, difficulty breathing, and even anaphylactic shock. IgE allergies can be identified by serum testing; it measures the intensity of the immune response that occurs when the possible allergen comes into contact with our blood.

By contrast, IgG food allergies can be better understood as food sensitivities. People having IgG allergic reactions may not show symptoms until several days after consuming the food. This means that some of us have IgG allergies that we are not even aware of. For this reason, it can be difficult to use traditional food allergy tests to detect IgG allergies. Instead, it may make more sense to embark on an elimination diet for a time in order to identify whether the absence of certain foods in your diet is associated with the absence of certain symptoms you experience.

People with IgG allergies usually have a different set of symptoms, typically longer-lasting and harder to detect than an IgE allergic reaction. Instead of having symptoms such as hives, itching, or swelling, somebody experiencing an IgG reaction might feel anxious or depressed, have headaches, feel bloated or constipated, feel tired or weak, or feel like their brain is foggy. If they have a diagnosis of another medical issue, such as irritable bowel syndrome or rheumatoid arthritis, their symptoms related to these diagnoses may be worse when they eat foods to which they are sensitive.​

Food Allergy Home Test

There are many home test kits for food allergies available to consumers. If you are interested in purchasing one that can test for a comprehensive list of food allergies, we recommend looking at this one. It tests for an immune response in a slightly different way than other serum testing and does not require consumption of any foods, so the risk to you is minimal.

Benefits of Food Allergy Tests

Food allergy tests are an essential and effective component of getting people answers about which foods are and are not safe for them (Boyce et al., 2011; Collins & Jackson, 2013). Without these tests, many people would be repeatedly exposed to foods that can cause them significant harm or even death. The research on food allergy tests conducted thus far suggests that testing done under the supervision of a doctor, or at a doctor’s office, is likely to be more effective and of higher quality than testing conducted in one’s own home (Wong et al., 2022). In addition to physician-led testing being of higher quality, it takes place in an environment where the doctor can ask relevant questions and consider your other physical and mental health symptoms to make sure that a food allergy diagnosis is not mistakenly given when another diagnosis would be more appropriate or accurate.

Food Allergy Causes

Why do we have food allergies in the first place? It seems that food allergies are related both to our genetics and to our experiences of not being exposed to certain foods as we grow up (Sampson et al., 2018). The genes we inherited from our parents may set us up to have allergic reactions to certain foods; we know this because studies of people who are twins have shown that people with more genes in common are more likely to share the same food allergy (Kivistö et al., 2019). At the same time, if our bodies do not get exposed to certain foods, we may become sensitized to them as well—a fact that has led some doctors to recommend exposing children early on to foods such as peanuts (Togias et al., 2017).

Food Allergy Symptoms & Signs​

A surprising sign that you may have a food allergy is if you have atopic dermatitis, more commonly known as eczema (Ramírez-Marín et al., 2022). For some children with eczema, the removal of foods such as eggs, milk, or peanuts may improve their eczema. Anybody considering eliminating foods from their diet to treat their eczema should still consult with a doctor before doing so (Ramírez-Marín et al., 2022).

The most common immediate symptoms of a food allergy reaction are itchy skin or hives, swelling in the face, sneezing or a runny nose, stomach pain, diarrhea, feeling dizzy or lightheaded, and difficulty breathing (Boyce et al., 2011). As we noted above, food sensitivities can result in a very different set of symptoms.​

Food Allergies: Delayed Reactions & Food Sensitivities

The delayed reaction to foods that we are sensitive to, but not allergic to, looks pretty different (Collins & Jackson, 2013). It is difficult for us, and even for doctors, to draw connections between delayed symptoms and food consumption (Turnbull et al., 2015). This may explain why many people who are ultimately found to be gluten-intolerant or have celiac disease may not realize it until well into adulthood (Fasano & Catassi, 2012).

Food Allergy List

The most common food allergies, according to one study, are (in order of frequency) egg whites, peanuts, egg yolks, milk, soy, and wheat (Sherenian et al., 2021). Another study noted that tree nuts, fish and shellfish, and dairy are also common food allergies (Sampson et al., 2012).

Food Allergy Treatment

Once the best practice for determining food allergies as described above has been followed, there are two primary options moving forward. The safest option seems to be refraining from eating the foods altogether, but there is some evidence that taking certain medications can protect people from the worst allergic reaction symptoms (Nurmatov et al., 2012).

Food Allergy Action Plan

So, to be clear, a good action plan for determining one’s food allergies would start with consulting a medical professional (Lieberman & Sicherer, 2010) and following evidence-based protocols for figuring out what you are allergic to. Using other methods or going it on your own puts you at risk of eating something you really shouldn’t or eliminating foods from your life unnecessarily. After that, I would recommend continuing to follow your physician’s recommendations regarding whether to treat your allergy or simply avoid the food(s).

Articles Related to Food Allergy Tests

​Want to learn more? Check out these articles:

Books & Products Related to Food Allergy Tests

If you’d like to keep learning more, here are a few books that you might be interested in.

Final Thoughts on Food Allergy Tests​

I hope this article helps you see that some aspects of food allergies are very clear while others aren’t. Immediate allergic reactions to foods should be pretty obvious, but there are lots of experiences we have that could result from a food sensitivity or from something else entirely. To my mind, this makes it important not to overthink the situation or go out of one’s way to find a food allergy (Bird et al., 2015), since other variables may be at play. Also, there is research to suggest that people perceive themselves to have food allergies at higher rates than they actually do have food allergies (Woods et al., 2002). All of this is to say, if you have not had alarming or very consistent allergic symptoms after eating a food, it may just be perfectly safe to eat.

If you’d like to know more about food allergies and food sensitivities, here is a video:​

Video: What To Know Before Trying At-Home Food Sensitivity Kits

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