Food Allergies

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Although food allergies may seem to be a modern problem, references to adverse reactions to food date back to Hippocrates and Chinese emperors from around 2700 BCE. However, there is an increasing prevalence of food allergies, especially in the United States and other countries. Despite some of the increases in diagnoses arising from better testing methods, most can be attributed in some part to changes in lifestyle and environmental factors, such as an increase in sanitization and the use of antibiotics. Chemicals in foods and changes in plants to increase their defenses may increase their potential for triggering allergies.

Allergy, Intolerance, or Sensitivity

Before going into detail about food allergies, it is important to differentiate between an allergy, an intolerance, and a sensitivity

Allergies occur due to an immunological response, often involving IgE antibodies but may also be non-IgE mediated, or cell-mediated, allergies or a combination. In westernized countries worldwide, an estimated 8% of children and 2% of adults have a food allergy. Reactions, such as rashes, swelling, difficulty breathing, and hives, happen with any exposure, and in severe cases, even the slightest exposure could still lead to a potentially deadly reaction, such as anaphylaxis.

Most instances of adverse reactions to food have more to do with food intolerance rather than an allergy, and it is estimated roughly 15 to 20 percent of the population has some type of food intolerance. Intolerances occur due to the components or toxins in the food, IgG antibodies, or something a person lacks, such as specific enzymes, which is the case in lactose intolerance. A food intolerance-based reaction may not occur every time that a person consumes a food, as there may be an element of dose-dependence in a reaction.

There is some debate as to what to call these type of reactions, and in many camps, the preferred nomenclature for food intolerance is sensitivity or hypersensitivity, although others place allergy and intolerance as two categories under the umbrella category of hypersensitivity. In functional medicine, the term food sensitivity is used to describe instances where an imbalance in the gut leads to immune dysfunction that can contribute to an allergic response to foods. This effect includes the development of IgG antibodies to foods, but it may also include delayed onset IgE-related responses or cell-mediated responses[i].

Celiac disease is generally categorized under a different category, as it is an autoimmune disorder triggered by gluten rathering than being considered an allergy or intolerance.

Here is a chart detailing the differences:

Allergies Intolerances Sensitivity
Prevalence 4 – 8% of children; 3 – 4% of adults 15 – 20% N/A
Symptoms & Reaction Wheezing, breathing difficulties, swelling, vomiting, rash, hives, anaphylaxis GI symptoms (nausea, vomiting, diarrhea, etc.) Delayed responses, often GI in nature but may include skin problems, migraines, mental disorders and more
Contributing Causes IgE antibodies and non-IgE (cell) mediated Non-allergy induced: Lack of enzymes, reactions to the components of the food; toxins in the food; IgG antibodies Imbalance in the gut affecting the immune system; IgG antibodies
Time to Reaction Immediate Hours to days Hours to days
Examples Milk, soy, shellfish, wheat, tree nuts, peanuts, eggs, etc. Lactose Intolerance, fructose intolerance, MSG, histamine intolerance Non-celiac gluten sensitivity
Antidote Avoidance of food; antihistamines; adrenaline (epipen) for anaphylaxis Avoidance of food; reduced dosage of food; removal of offending substance (lactose-free milk); supplement of the necessary enzyme (lactase) Avoidance of food; healing the underlying gut imbalance

Common Food Allergies

The most common food allergies differ depending on the location and culture of the population, with countries and regions having their own lists. In the U.S., the most common ones include:

  • Cow’s milk
  • Eggs
  • Peanuts
  • Tree nuts (top 9 include walnuts, pistachios, pecans, cashews, almonds, macadamias, pine nuts, pecans, and Brazil nuts; the USDA also considers coconut and several others as tree nuts)
  • Soy
  • Wheat
  • Fish
  • Shellfish

In the large cohort study mentioned above, the most common allergy was peanut with a prevalence of 2.6%, followed by milk at 2.2%, egg at 1.8%, shellfish at 1.5% and soy at 0.7%.

Vitamin D and Food Allergies

Vitamin D plays a key role in immune health, as well as other aspects of overall wellness. Another role it may play is in the development of food allergy. Epidemiological evidence points to an association between vitamin D levels and food allergy incidence. One study found that infants with a vitamin D level at or below 50 nmol/L were 10 times as likely to develop multiple food allergies, 11 times as likely to have a peanut allergy, and 4 times more likely to have an egg allergy compared to those with adequate vitamin D levels.

Intestinal Permeability, the Microbiome, and Food Allergies

It probably comes as no surprise to you that the microbiome plays some role in the development of food allergies, due to the commensal bacteria’s important role in so many health conditions. One study compared the gut microbiome of children with diagnosed IgE mediated food allergies with that of their siblings who did not have a food allergy as well as non-allergic controls. There was a difference in those who had food allergies, namely in the Clostridia and Firmicutes phylum.

There have been some studies looking into whether probiotics can prevent or treat food allergies, but the results have been mixed and the trials have mainly been in vitro and/or on animal models. A recent mouse study found that a mixture of several probiotics strains significantly inhibited the secretion of IgE and certain inflammatory cytokines, demonstrating a potential preventative effect. Another mouse study found that a bifidobacterium infantis strain attenuated the inflammation from an allergic response and inhibited the secretion of IgE. One Polish study on humans found that although probiotics did not have an effect on young children, but it did help with adolescents over the age of 14.

Intestinal permeability may also be at play in the development of food allergies. One study on over a hundred children with confirmed milk and/or egg allergies found that 38 percent still had increased intestinal permeability (based on a breath test) even while on strict elimination diets and no symptoms, which may point to an intrinsic role that it plays in at least some people. 

Nutritional Management of Food Allergies

One of the easiest ways to address food allergies or intolerances nutritionally is to remove the offending food from your diet. Below is a list of the common diets used to treat food allergies and intolerances:

One study found that after four weeks on an elimination diet, 98.4% of the children in the experiment with non-IgE mediated gastrointestinal food allergies experienced improvement. When adequately implemented to ensure adequate nutrition, there was no negative impact on the nutritional status or growth of the children.

One consideration of an elimination diet is potential malnutrition, especially in those with multiple food allergies. To prevent malnutrition, you must incorporate complementary foods to get the same nutrients as the one eliminated from the diet. Below is a list of the nutrient deficiencies most at risk for certain foods:

  • Fish: Iron and zinc
  • Peanuts: Chromium, magnesium, manganese, niacin, vitamin E
  • Soy: Thiamin, Riboflavin, pyridoxine, folate, calcium, phosphorus, magnesium, zinc, and iron
  • Grain: Riboflavin, niacin, iron, thiamine, and folate (when fortified)
  • Eggs: Riboflavin, vitamin B12, biotin, pantothenic acid, and selenium
  • Milk: Phosphorus, calcium, vitamin B12, pantothenic acid, riboflavin, vitamin D, and vitamin A

Luckily, these nutrients can be found in other food sources.

An important component of preventing and mitigating food allergies at any age is to take care of your gut, especially to reduce any intentional permeability and ensure a balanced microbiome.


It is possible to live a healthy and nutritious life with a food allergy. When embarking on a temporary elimination diet or a long-term diet that excludes a food to which you or your child is allergic, especially if it is a nutrient-rich staple in the diet, it is important to work with a nutritional professional to learn the ways to ensure that you get the necessary nutrients without consuming that food. This is vital for children to ensure they have the essential nutrients for proper development.

[i] Hyman, M. (2010). “Diet and Nutrition.” Chapter 26: Clinical Approaches to Environmental Outputs. In Jones, D. (ed.) Textbook of Functional Medicine. Pg. 369.




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