Signs, Symptoms, & Home Kits

 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.​

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.​

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 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.

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.​

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:​

• Bird, J. A., Crain, M., & Varshney, P. (2015). Food allergen panel testing often results in misdiagnosis of food allergy.  The Journal of Pediatrics, 166(1), 97–100.
• Boyce, J. A., Assa’ad, A., Burks, A. W., Jones, S. M., Sampson, H. A., Wood, R. A., . . . & Schwaninger, J. M. (2011). Guidelines for the diagnosis and management of food allergy in the United States: summary of the NIAID-sponsored expert panel report. Journal of the American Academy of Dermatology, 64(1), 175–192.
• Collins, A. M., & Jackson, K. J. (2013). A temporal model of human IgE and IgG antibody function. Frontiers in Immunology, 4, 235.
• Fasano, A., & Catassi, C. (2012). Celiac disease. New England Journal of Medicine, 367(25), 2419–2426.
• Kivistö, J. E., Clarke, A., Dery, A., De Schryver, S., Shand, G., Huhtala, H., . . . & Ben-Shoshan, M. (2019). Genetic and environmental susceptibility to food allergy in a registry of twins. Journal of Allergy and Clinical Immunology: In Practice, 7(8), 2916–2918.
• LaHood, N. A., & Patil, S. U. (2019). Food allergy testing. Clinics in Laboratory Medicine, 39(4), 625–642.
• Lieberman, J. A., & Sicherer, S. H. (2010). The diagnosis of food allergy. American Journal of Rhinology & Allergy, 24(6), 439–443.
• Nurmatov, U., Venderbosch, I., Devereux, G., Simons, F. E. R., & Sheikh, A. (2012). Allergen‐specific oral immunotherapy for peanut allergy. Cochrane Database of Systematic Reviews, (9).
• Pyrhönen, K., Hiltunen, L., Näyhä, S., Läärä, E., & Kaila, M. (2011). Real‐life epidemiology of food allergy testing in Finnish children. Pediatric Allergy and Immunology, 22(4), 361–368.
• Ramírez-Marín, H. A., Singh, A. M., Ong, P. Y., & Silverberg, J. I. (2022). Food allergy testing in atopic dermatitis. JAAD International, 9, 50–56.
• Sampson, H. A., O’Mahony, L., Burks, A. W., Plaut, M., Lack, G., & Akdis, C. A. (2018). Mechanisms of food allergy. Journal of Allergy and Clinical Immunology, 141(1), 11–19.
• Sampson, H. A., Van Wijk, R. G., Bindslev-Jensen, C., Sicherer, S., Teuber, S. S., Burks, A. W., . . . & Chinchilli, V. M. (2012). Standardizing double-blind, placebo-controlled oral food challenges: American Academy of Allergy, Asthma & Immunology–European Academy of Allergy and Clinical Immunology PRACTALL consensus report. Journal of Allergy and Clinical Immunology, 130(6), 1260–1274.
• Sherenian, M. G., Kothari, A., Biagini, J. M., Kroner, J. W., Baatyrbek Kyzy, A., Johannson, E., . . . & Khurana Hershey, G. K. (2021). Sensitization to peanut, egg or pets is associated with skin barrier dysfunction in children with atopic dermatitis. Clinical & Experimental Allergy, 51(5), 666–673.
• Togias, A., Cooper, S. F., Acebal, M. L. Assa’ad, A., Baker, J.R., Beck, L.A., . . . & Boyce, J. A. (2017). Addendum guidelines for the prevention of peanut allergy in the United States: report of the National Institute of Allergy and Infectious Diseases–sponsored expert panel. Journal of Allergy and Clinical Immunology, 139, 29–44.
• Turnbull, J. L., Adams, H. N., & Gorard, D. A. (2015). The diagnosis and management of food allergy and food intolerances. Alimentary Pharmacology & Therapeutics, 41(1), 3–25.
• Wong, A. W. Y., White, H. E. G., Plant, A., Shipman, A. R., & Shipman, K. E. (2022). Issues surrounding consumer‐bought food‐allergy testing. Clinical and Experimental Dermatology, 47(3), 547–552.
• Woods, R. K., Stoney, R. M., Raven, J., Walters, E. H., Abramson, M., & Thien, F. C. K. (2002). Reported adverse food reactions overestimate true food allergy in the community. European Journal of Clinical Nutrition, 56(1), 31–36.