Health & Science

What Are Food Allergies, Food Intolerances, and Food Sensitivities?

December 22, 2021

Patty James

A food allergy occurs when the immune system mistakenly “flags” a food protein as harmful and responds by attacking it, causing an allergic reaction that can range from mild to severe or life-threatening. Food allergies are rising globally and nationally, primarily in westernized and industrialized countries. An estimated 32 million people in the United States have a food allergy.

In addition to the rise in food allergy, we also see an increase in the severity of symptoms. You can develop a food allergy when you consume or are exposed to an allergen (i.e., protein in peanuts) that your body mistakenly recognizes as harmful, which in turn leads to the immune system producing disease-fighting IgE (or Immunoglobin E) antibodies – this process is known as sensitization. At this point, no symptoms occur.

The process of sensitization primes the immune system to react to the offending allergen once it is ingested again. Suppose you, for example, are exposed to the offending allergen (or food) again. In that case, your immune system reacts by releasing allergen-specific IgE antibodies and other chemicals such as histamines, resulting in inflammation, pruritis (itching), and contraction of the smooth muscles in the blood vessels, gastrointestinal and respiratory tracts.

There are three ways in which food allergies can be categorized:

  • IgE-mediated food allergy (discussed above) – the most common type of food allergy, the immune system triggers the development of an antibody called immunoglobin E (IgE). Symptoms typically occur within seconds or minutes after consuming the offending food
  • Non-IgE-mediated food allergy – an allergic reaction not associated with the development of immunoglobin E but by other cells in the immune system. Often difficult to diagnose since symptoms take longer to present – up to several hours
  • Mixed IgE and non-IgE-mediated food allergies – some individuals may experience symptoms of both types of food allergy

Other related food allergies involve a person experiencing itchiness in their mouth and throat and occasional swelling, usually mild, immediately after eating fresh fruit or vegetables – this is known as oral allergy syndrome (or pollen-food syndrome). This syndrome is caused by allergy antibodies mistaking specific proteins in fresh fruits, nuts, or vegetables for pollen. This condition is non-serious and can be mediated by cooking fruits and vegetables.


What Are Food Intolerances?

food intolerance

Food intolerance occurs when an individual’s digestive system is unable to properly break down the food, typically due to the absence of an enzyme needed to digest the food (i.e., the lack of lactase in lactose-intolerant persons). Food intolerance is common, and almost everyone at one point has experienced intolerance to certain foods. Typically, those who have intolerances need to eat larger amounts of food to trigger a tolerance.

What Are Food Sensitivities?

Food sensitivities occur when exposure to specific foods facilitates an immune reaction that results in many symptoms. These symptoms are not usually life-threatening but can be disruptive. Gluten is the best example of food sensitivity. It should be noted that people with food sensitivities are not at risk for anaphylaxis.


Important Considerations for Food Allergy, Food Tolerance, and Food Sensitivities

An important consideration to be aware of is the relatedness of food sensitivity with non-IgE mediated allergy, meaning that food sensitivity is essentially the “same” as a non-mediated food allergy, but this association is tricky. Often health professionals can inadvertently downplay the seriousness of non-mediated IgE food allergies and are often considered not “true allergies.”

Mun Cho, a registered dietitian, and parent of children with both IgE-mediated and non-IgE-mediated allergies calls for a change in the way we label non-IgE-mediated allergies and move away from the false pretense that those with non-IgE-mediated food allergies can have trace amounts of an offending allergen.

Although non-IgE- mediated food allergies are non-fatal, in most cases, people suffering from this type of allergy have to take every precaution to avoid consumption of the offending allergen. It should be noted that food sensitivity and food intolerance are often used interchangeably and sometimes separately. For this article, the two terms will be separate.


What Is the Difference Between Food Allergies, Food Intolerance, and Food Sensitivities?

food sensitivity

It is essential to understand and differentiate the difference a food allergy, food intolerance, and food sensitivity. Each has different ways or mechanisms in which they present themselves in the body.

Food Allergy vs. Food Intolerance

The main difference between food allergy and food intolerance is that food allergy involves the immune system and food intolerance affects the digestive system. Food intolerance is dose-related, and symptoms may not occur unless large quantities of the food are consumed or are eaten more frequently.

In contrast, symptoms of food allergies can be triggered by a small amount of food and occur every time the food is ingested or eaten. The symptoms of a food allergy are more severe and can be life-threatening.

Food Allergy vs. Food Sensitivities

Food sensitivities differ from food allergies because they involve both the digestive and immune systems. Food allergies only affect the immune system.

Food Intolerance vs. Food Sensitivities

Food intolerances are often caused by difficulties in digesting or breaking down specific proteins, such as lactose, whereas food sensitivities involve an immune reaction that results in various symptoms that can be disruptive.


Symptoms of Food Allergies

symptoms of food allergy

The symptoms of food allergies can range from mild to severe or even life-threatening. The severity of a food allergy can vary from person to person. Symptoms from a food allergy can develop within minutes or as long as two hours.

Some examples of symptoms of food allergies include the following:

  • Tingling or itching in the mouth
  • Hives, itching
  • Vomiting and/or stomach cramps
  • Shortness of breath
  • Wheezing, nasal congestion, or trouble breathing
  • Dizziness, lightheadedness, or fainting
  • Swelling of the tongue, affecting the ability to talk or breathe
  • Swelling of the lips, face, tongue, and throat or other parts of the body (or angioedema)

Anaphylaxis is another symptom that some people with food allergies may experience. Anaphylaxis is a serious, life-threatening allergic reaction to food. Symptoms of anaphylaxis include:

  • Constriction and tightening of the airways
  • Swollen throat
  • Shock with a severe drop in blood pressure
  • Rapid pulse
  • Dizziness, lightheadedness, and loss of consciousness

In the event of anaphylaxis, epinephrine (i.e., EpiPen, Auvi-Q, Adrenaclick) must be administered appropriately and promptly.

Symptoms of Food Intolerance and Sensitivity

Food intolerances can occur for several reasons. The first is the absence of the enzyme needed to break down a certain protein in the digestive system. For example, some people are missing the enzyme lactase, which is responsible for breaking down lactose – individuals missing this key enzyme are considered lactose intolerant.

Sensitivity to food additives is another cause of food intolerance; for example, some people may be sensitive to sulfites used to preserve dried fruits, canned goods, and wine. These additives may even trigger asthmas attacks in some people.  The symptoms of food intolerance include:

  • Nausea
  • Stomach pain
  • Gas, cramps, or bloating
  • Vomiting
  • Heartburn
  • Diarrhea
  • Headaches
  • Histamine toxicity – Certain fish, such as tuna or mackerel, that are not refrigerated properly and that contain high amounts of bacteria may also contain high levels of histamine that trigger symptoms similar to those of food allergy. Rather than an allergic reaction, this is known as histamine toxicity or scombroid poisoning.

As discussed previously, food sensitives are thought to appear when an “exposure to specific foods may create an immune reaction that generates a multitude of symptoms.” These symptoms are non-life threatening and include:

  • Joint pain
  • Stomach pain
  • Fatigue
  • Rashes
  • Brain fog


Most Common Allergens

food allergens

Many allergens trigger food sensitivity, tolerance, and allergy. However, the 9 most common allergens include:

  • Milk
  • Eggs
  • Peanuts
  • Gluten
  • Tree nuts (such as almonds, cashews, walnuts)
  • Fish (such as bass, cod, flounder, salmon)
  • Shellfish (such as crab, lobster, shrimp)
  • Soy
  • Wheat
  • Sesame

You can find alternatives to many of these common allergens. For example, almond milk as a substitute for cow’s milk or oat milk as a substitute for almond milk if you have a sensitivity to nuts. Coconut milk may also be a great alternative for those who have sensitivities or allergies to both nuts and cow’s milk.

How Is a Food Sensitivity Contracted?

The gut microbiota contains bacteria, viruses, and other microorganisms that are crucial to the health of human beings. It is well-established that disruptions in the gut microbiota can negatively impact the immune response.

Likewise, evidence of the microbiota in establishing and maintaining food tolerance is firmly established. We know that environmental factors, diets, and drugs (i.e., antibiotics) can increase the risk of developing a food allergy by promoting changes in the gut microbiota.

Some environmental factors that contribute to disruptions in the microbiota of the gastrointestinal tract include

  • Pregnancy factors such as the method of delivery (cesarean vs. vaginal) can impact the microbiota of infants; for example, infants born via cesareans have a higher incidence of food allergy
  • Antibiotic use, inappropriate or overuse of these drugs can affect microbiota, for example
  • Diet, western diets that are high in sugar, low in fiber can alter gut microbiota

food sensitivity

It is worth noting that the gut microbiota is unique to each individual and contributes to how a person fights disease, digests food, and even their mood and physiological processes.

A condition that is related to gut microbiota is leaky gut syndrome. In fact, it is believed that a leaky gut may be caused by altered microbiota in the gastrointestinal tract. In our intestines, we have a lining that covers more than 4,000 square feet of surface area.

The purpose of this lining is to control what gets into our bloodstream. However, if this lining is damaged or unhealthy, it may have large cracks or holes that allow partially digested food, toxins, and bugs to penetrate the tissues and enter the bloodstream.

This can trigger inflammation and even lead to changes in the gut microbiota, leading to a host of issues in the digestive tract and other parts of the body.

Gut microbiota also plays a role in the development of Celiac Disease, which is an autoimmune condition that damages the lining of the small intestine. This damage results from eating gluten found in wheat, rye, barley, oats, and foods made with these items.

Due to the damage, the intestine is not able to absorb nutrients from food. This damage to the intestine lining may lead to inflammation and affect other parts of the body.


There is some evidence to suggest that genetics contribute to the development of food tolerances and allergies. For example, lactose intolerance is more prevalent in certain racial/ethnic groups – African Americans, Asian Americans, and Native Americans have considerably higher rates of lactose intolerance, whereas lactose intolerance appears to be less common among Americans of Northern European ancestry.

Lactose intolerance can be caused by the LCT gene, which is controlled by a DNA sequence called a regulatory element. This element is located within a nearby gene called MCM6. Some people inherit changes or variations in this element that allow them to sustain lactose production in the small intestine. People without these changes experience a reduction in the ability to digest lactose as they age.

Although genetics alone cannot justify the increasing rate of food allergy, there is evidence that exists for genetic predisposition of food allergies based on family aggregation.

Celiac Disease, the autoimmune condition discussed earlier, occurs in genetically susceptible individuals who have HLA-DQ2 and/or HLA-DQA genotypes.


There are a number of tests used to diagnose food allergies. Before any administration of tests, you may be asked by your primary care doctor or allergist about your medical history, such as:

  • What symptoms did you experience?
  • How long did they last after eating the offending food?
  • What food did you eat, and how much?
  • How long did it take for you to develop symptoms?

food intolerance

After your history is taken, your health care provider may order skin tests and/or blood tests that will be able to identify whether allergen-specific immunoglobulin (IgE) antibodies are present in your body.

Tests for food allergies include:

  • Skin-prick tests – usually results are available in about 20 minutes –
    1. Liquid containing a small amount of food allergen
    2. Liquid placed on the skin of your arm or back
    3. Skin pricked with a small, sterile probe that allows for liquid to seep under the skin
    4. Not painful but can be uncomfortable
    5. Considered positive if a bump resembling that of a mosquito bite develops at the site of their food, allergen was placed
    6. You will also receive a skin prick with a liquid that does not contain the suspected allergen
  • Blood tests – less exact than skin tests; measures the amount of IgE antibody of food allergen tested. Result available in about a week
  • Oral food challenge – allergist may recommend; the patient is fed tiny amounts of suspected food in increasing doses over time; followed by a few hours of observation; must be done under strict medical supervision; helpful when a patient has an unclear or limited medical history or if skin and blood tests are inconclusive; can be used to see if you have outgrown an allergy

You may wonder how accurate the tests for food sensitivity or food allergy are — the oral food challenge is the most accurate way to make a food allergy diagnosis.


The primary treatment of food allergies consists of managing the signs and symptoms. It is worth noting that food allergies have no cure. However, many children can grow out of their food allergies — food allergies in adults tend to be longer-lasting and may persist over a lifetime.

One way to mitigate the signs and symptoms of a food allergy is to avoid the foods that cause allergic reactions simply. It is useful to know how to read the nutritional label on food products to do this. Nutritionists and dietitians can help with instruction in this area.

Recent advancements and discoveries in the immunological processes underlying food allergy have allowed for food allergy management through immunotherapy. Food allergy immunotherapy (FAIT) “is aimed to achieve a permanent unresponsiveness to food allergens or at least to increase the threshold dose of food necessary to trigger an allergic reaction.” The objective of immunotherapy is to guarantee a certain degree of protection from accidental exposure and improve quality of life.

Different methods of immunotherapy include oral (OIT), sublingual (SLIT), and epicutaneous (EPIT). The OIT consists of the ingestion of low and progressively increasing daily doses of the allergen, SLIT involves the administration under the tongue, and EPIT is administered on the surface through special adhesives. OIT is the most effective method of immunotherapies.


How Foogal Can Help

If you have food allergies, food intolerances, or sensitivities, Foogal can help with that. We have filters for common allergies such as dairy, eggs, nuts and, gluten. Foogal is dedicated to ensuring that you eat a healthy diet that is both easy and delicious as well as accommodating to your unique health needs. You can find our app on AppStore or Google Play.