A Closer Look at Food allergies and oral allergy syndrome

Have you or someone you know been diagnosed with a food allergy?  Do you find you react to certain foods and suspect that you may have an allergy but are not sure?  Are you curious about what food allergies are?  If you answered yes to any of these, this article might provide some general answers to some of your questions until you are able to speak with your physician about your individual health needs.

Allergies

What exactly is an allergy? 

In short, allergies are an immune system reaction to a protein that is usually a harmless substance. Allergic reactions can range from mild to anaphylactic (life-threatening).

What are the most common food allergens?

According to the Centers for Disease Control and Prevention, allergies affect approximately 8 % of children and 4% of adults in the United States (Food Allergies | Healthy Schools | CDC, n.d.; Gupta et al., 2018). Health Canada reports that approximately 8.7% of children 0-17 years and 9.5% of adults in Canada self-report a food allergy (2020: Research Related to the Prevalence of Food Allergies and Intolerances – Canada.Ca, n.d.).  The Canadian Society of Allergy and Clinical Immunology reports that approximately 2% of Canadians are at risk of anaphylaxis from food (Anaphylaxis in Schools & Other Settings, n.d.)

According to the American Academy of Allergy, Asthma, and Immunology, the top allergens (accounting for 90% of all reactions) in the United States as of January 2023 are eggs, cow’s milk, peanuts, tree nuts, fish, shellfish, wheat, soy, and sesame (Food Allergies | Causes, Symptoms & Treatment | ACAAI Public Website, n.d.). 

According to the American College of Allergy, Asthma, and Immunology, the Food Allergy Labeling and Consumer Protection Act of 2004 (FALCPA) requires manufacturers of packaged foods produced in the United States to identify, in simple, clear language, the presence of any of the eight most common food allergens – milk, egg, wheat, soy, peanut, tree nut, fish and crustacean shellfish – in their products. The presence of the allergen must be stated, even if it is in an additive or flavouring (Food Allergies | Causes, Symptoms & Treatment | ACAAI Public Website, n.d.).

In Canada, the priority allergens that must always be identified on food labels by their common names are:  wheat, triticale, seafood (fish and shellfish), mustard, peanut, tree nut (almond, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pine nuts, pistachios, walnuts), milk, egg, sesame, sulphites, and soy (Allergens and Gluten Sources Labelling – Canada.Ca, n.d.; Anaphylaxis in Schools & Other Settings, n.d.).

Some goods also may be labeled with precautionary statements, such as “may contain,” “might contain,” “made on shared equipment,” “made in a shared facility” or some other indication of potential allergen contamination. In neither Canada nor the USA, there are no laws or regulations requiring those advisory warnings and no standards that define what they mean (Food Allergies | Causes, Symptoms & Treatment | ACAAI Public Website, n.d.; Tips for Avoiding Common Allergens in Food – Canada.Ca, n.d.).

What are the symptoms?

Allergic reactions usually occur within 2 hours of exposure; however, they can occur up to 24 hours later (Food Allergy | AAAAI, n.d.). Unfortunately, it is impossible to know if an allergic person will have a mild or severe reaction after exposure.  The same allergen may cause mild hives one time and anaphylaxis the next, followed by a mild reaction on the third exposure.  There’s just no way of knowing which reaction a person may have, so it’s important that all allergies are treated as though they’re severe(Tips for Avoiding Common Allergens in Food – Canada.Ca, n.d.). 

The most common symptoms are: 

• Itchy mouth, throat, eyes, nose
• Runny nose
• Nausea
• Vomiting
• Diarrhea
• Difficulty breathing
• Hives
• Teary eyes

In an anaphylactic reaction, swelling (often closing off the airway), low blood pressure, and hives are the most common symptoms; however, shock can also occur.  Symptoms usually start 5-30 minutes after exposure. Anaphylaxis is a life-threatening condition that can be fatal(Anaphylaxis in Schools & Other Settings, n.d.; Oral Allergy Syndrome Symptoms, Diagnosis & Treatment | AAAAI, n.d.).

To know more about this severe allergic reaction, check out my post about What Is Anaphylaxis and How Is Treated.

What happens in my body when I’m having an allergic reaction?

When an allergic person is exposed to an allergen, their immune system views it as a foreign invader and mounts a defense against it. This is done through the activation of specialized white blood cells known as immunoglobulin E (IgE) antibodies. These IgE antibodies then attach to another type of white bloods cell known as mast cells found in your skin, lungs, nose, and blood, digestive tract, causing the release of chemicals, including histamine, to fight off the “invasion”.  Histamine tries to defend the body against the “invader” by causing several things to happen, such as increased blood flow, swelling, and mucous production, the symptoms that we normally associate with an allergic reaction(Food Allergies | Causes, Symptoms & Treatment | ACAAI Public Website, n.d.; Food Allergy | AAAAI, n.d.).  

How are allergies treated?

Allergic reactions are usually treated with antihistamines when they are mild.  In the case of severe reactions, epinephrine injection, and immediate medical attention is the treatment (Food Allergies | Causes, Symptoms & Treatment | ACAAI Public Website, n.d.).

Oral allergy syndrome (OAS)

What is oral allergy syndrome?

Oral allergy syndrome is sometimes referred to as pollen fruit syndrome. It is a reaction in the mouth or throat of a person allergic to latex or pollen after eating raw food with a similarly shaped protein.  Because it is just a similarly shaped protein and not the protein that the person is allergic to, exposure usually just causes itchiness in the mouth and/or throat. It can, however, occasionally lead to an anaphylactic reaction in those with severe allergies(Oral Allergy Syndrome Symptoms, Diagnosis & Treatment | AAAAI, n.d.).  

Who is affected by OAS?

OAS is thought to occur in 50-75% of adults with birch tree pollen allergies (Oral Allergy Syndrome Symptoms, Diagnosis & Treatment | AAAAI, n.d.). It can also occur in those with allergies to ragweed, timothy grass, and mugwort. It is interesting to note that cooking denatures (changes the shape) most proteins so that they do not cause the symptoms of OAS, meaning that it may not be possible for someone to eat a raw apple, but they can enjoy apple pie.

What are the symptoms?

Because it is just a similarly shaped protein and not the protein that the person is allergic to, exposure usually just causes itchiness in the mouth and/or throat. It can, however, occasionally lead to an anaphylactic reaction in those with severe allergies(Oral Allergy Syndrome Symptoms, Diagnosis & Treatment | AAAAI, n.d.).  

How is OAS treated?

There’s no specific treatment for oral allergy syndrome. Avoiding food that causes intolerable symptoms in raw forms is the most common way to manage this. If you experience severe symptoms, your allergist may prescribe an epinephrine auto-injector.

Testing for allergies

The American Academy of Asthma, Allergy, and Immunology recommends that anyone experiencing allergic symptoms be tested by an allergist/immunologist to determine the best type of testing for your symptoms(Food Allergy | AAAAI, n.d.).  

There is scientific evidence to show that traditional skin prick and intradermal testing, are good first steps to help narrow down which substances may be responsible for an allergic reaction when the source is unclear, i.e., environmental allergens.

There is also good evidence for medically supervised oral challenges (done in a medical clinic or hospital setting) where incrementally larger amounts of an allergen are introduced, starting from a very small amount being held in the mouth to the consumption of a whole food item over the course of several hours. IgE blood testing also has sound scientific evidence as a way to test for food allergies (Allergy Testing | Skin Testing | AAAAI, n.d.). 

The American Academy of Asthma, Allergy, and Immunology, European Academy of Allergy and Clinical Immunology, nor the Canadian Society of Allergy and Clinical Immunology recommends the use of IgG tests as there is not sufficient scientific evidence to support that they actually test what they claim to test. In fact, high levels of IgG in the blood following exposure to a food may actually indicate tolerance to that food and not intolerance (Allergy Testing | Skin Testing | AAAAI, n.d.; Carr et al., 2012; Stapel et al., 2008). 

Find Help

Where do I find an allergist or immunologist to get testing and advice?

• In the United States, you can use the “find an allergist” tool on the AAAAI website here.
• In Canada, you can find an allergist here.

Where do I find additional help?

The FDA provides guidance to the food industry, consumers, and other stakeholders on the best ways to assess and manage allergen hazards in food.

The Government of Canada has developed a series of consumer information packages for the priority allergen, which can be accessed here.

Food Allergy Canada is an advocacy group with a lot of great resources with a health care advisory board composed of allergists and immunologists.

American Academy of Nutrition and Dietetics can link you to a registered dietitian to help you navigate eating with restrictive or multiple food allergies and intolerances, as well as having some good consumer resources.

Dietitians of Canada can link you to a registered dietitian to help you navigate eating with restrictive or multiple food allergies and intolerances, as well as having some good consumer resources.

References:

2020: Research Related to the Prevalence of Food Allergies and Intolerances – Canada.ca. (n.d.). Retrieved January 6, 2023, from https://www.canada.ca/en/health-canada/services/food-nutrition/food-safety/food-allergies-intolerances/food-allergen-research-program/research-related-prevalence-food-allergies-intolerances.html

Allergens and gluten sources labelling – Canada.ca. (n.d.). Retrieved January 7, 2023, from https://www.canada.ca/en/health-canada/services/food-allergies-intolerances/avoiding-allergens-food/allergen-labelling.html

Allergy Testing | Skin Testing | AAAAI. (n.d.). Retrieved January 6, 2023, from https://www.aaaai.org/Tools-for-the-Public/Conditions-Library/Allergies/Allergy-Testing

Anaphylaxis in Schools & Other Settings. (n.d.). Retrieved January 6, 2023, from https://csaci.ca/flip/en/mobile/index.html#p=10

Carr, S., Chan, E., Lavine, E., & Moote, W. (2012). CSACI Position statement on the testing of food-specific IgG. Allergy, Asthma, and Clinical Immunology : Official Journal of the Canadian Society of Allergy and Clinical Immunology,8(1), 12. https://doi.org/10.1186/1710-1492-8-12

Food Allergies | Causes, Symptoms & Treatment | ACAAI Public Website. (n.d.). Retrieved January 7, 2023, from https://acaai.org/allergies/allergic-conditions/food/

Food Allergies | Healthy Schools | CDC. (n.d.). Retrieved January 6, 2023, from https://www.cdc.gov/healthyschools/foodallergies/index.htm

Food Allergy | AAAAI. (n.d.). Retrieved January 6, 2023, from https://www.aaaai.org/Tools-for-the-Public/Conditions-Library/Allergies/Food-allergy-TTR

Gupta, R. S., Warren, C. M., Smith, B. M., Blumenstock, J. A., Jiang, J., Davis, M. M., & Nadeau, K. C. (2018). The Public Health Impact of Parent-Reported Childhood Food Allergies in the United States. Pediatrics, 142(6). https://doi.org/10.1542/peds.2018-1235

Oral Allergy Syndrome Symptoms, Diagnosis & Treatment | AAAAI. (n.d.). Retrieved January 6, 2023, from https://www.aaaai.org/Tools-for-the-Public/Conditions-Library/Allergies/Oral-allergy-syndrome-(OAS)

Stapel, S. O., Asero, R., Ballmer-Weber, B. K., Knol, E. F., Strobel, S., Vieths, S., & Kleine-Tebbe, J. (2008). Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report. Allergy: European Journal of Allergy and Clinical Immunology, 63(7), 793–796. https://doi.org/10.1111/J.1398-9995.2008.01705.X

Tips for avoiding common allergens in food – Canada.ca. (n.d.). Retrieved January 7, 2023, from https://www.canada.ca/en/health-canada/services/food-allergies-intolerances/avoiding-allergens-food/tips-avoiding-common-allergens-food.html