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What is a Food Allergy, Anyway?

Many Different Immune Reactions to Food

Within the last 10 years, food allergies have entered our lives at a record pace.  So quickly, in fact, that research and medical communities are sometimes behind the experiences of their patients.  Patients are self diagnosing, eliminating certain foods and at times feeling better as a result.  But at other times patients feel more confused, and their health is compromised.

An underlying problem is that the word "food allergy" means different things to different people.  In truth, there are many different immune reactions to foods.  Thus, there are different types of "food allergies," as well as non-immune reactions to foods.

If doctor, patient, nutritionist, family member, friend, etc., speak the same language, Tender Foodies can more quickly become properly diagnosed.  We can communicate more clearly about the dangers of food allergies within their appropriate contexts.  We can better understand our risks.  We can more clearly define our individual needs -- for ourselves and for our social circles.

With the proper knowledge, we can heal more quickly. 

Please Note:  This page is not for self-diagnosis, but should be used to communicate with your doctor, or to help you find the right doctor for you.

 See also:  10 Steps to Help You Get Started



A heartfelt thanks to the medical professionals who are guest contributers to this page.

A Work in Progress:  This page is a work in progress that we will continually build.  Tender Palate is working with experts on multiple allergies and from different disciplines (with more experts to come).  With their help, we can speak the same language and further shorten the food allergy learning curve.

Sheila George, M.D., C.A.

Dr. George is a family medicine practitioner.  Her practice consists of metabolic and complementary medicine with a focus on treating chronic degenerative diseases and cancer. Treatment strategies include nutritional and dietary therapy, supplements, Chinese herbs, and acupuncture.  Her extensive, wholistic work with the immune system and nutrition is the expertise she brings to the Tender Palate community.


Alessio Fasano, M.D.

Alessio Fasano, M.D., is the director of the University of Maryland Center for Celiac Research, professor of pediatrics, medicine and physiology at the University of Maryland School of Medicine and director of the Mucosal Biology Research Center at the University of Maryland School of Medicine.  Dr. Fasano is an expert on gluten/wheat allergies and celiac disease.  In 2011, he led the research team who discovered a new immune reaction called "gluten sensitivity".


Types of Food Allergies

1. Classic Food Allergy 
(Immediate Hypersensitivity IgE response)

Immune Reaction:  The classical allergic reaction to food is often referred to as a "true food allergy" and involves two components of the immune system:

  1. IgE antibodies which circulate through the blood and
  2. Mast cells which is found in all tissues of the body

Before you can have an allergic reaction to a food allergen, you need to have been previously exposed to that food allergen. You need to have been sensitized to that food.  At that initial exposure the allergen stimulates lymphocytes in the body to produce IgE antibodies that are specific for the allergen. The IgE specific for the allergen then attaches to the mast cells in different tissues in the body. The next time the person eats that food allergen, it attaches to the IgE antibody-mast cell complex, which it previously helped to produce. This causes a release of histamine from the mast cells.

Causes:  There are 8 foods that are the most common causes for the Classic Food Allergy:  wheat, dairy, eggs, soy, peanuts, tree nuts, fish and shellfish.

Symptoms:  The symptoms vary depending on the tissue that is affected. The symptoms can range from itching, hives, difficulty breathing, asthma, nausea, diarrhea, abdominal pain, to anaphylaxis (a severe reaction to the allergen), and possibly death.

Timing:  The classic immediate type IgE allergy reaction occurs within minutes to several hours after exposure to the allergen.

Testing(we are currently working on this.  Stay tuned.)

Treatment:  Eliminate foods containing the allergen (and all contact with those foods).  Discuss the need and use of an Epi-pen with your doctor.

Number of people affected:  15 million (U.S. alone)


What is Anaphylaxis (Anaphylactic Shock)?:  "Anaphylaxis (pronounced ana-fill-axis) is a serious allergic reaction that is rapid in onset and may cause death.  Common causes of anaphylaxis include food, medication, insect stings, and latex. Food allergy is believed to be the leading cause of anaphylaxis outside the hospital setting. The CDC reported that food allergies result in over 300,000 ambulatory-care visits a year among children."

~Food Allergy & Anaphylaxis Network



2. Delayed Hypersensitivity T-cell Mediated Response (non-IgE response)

Immune Reaction:
  The mechanism involves the recruitment of lymphocytes into the tissue activated by the allergen. This sets off a cascade of events including the production of inflammation.

Causes: The 8 most common foods are the same as the Classic Food allergy:  wheat, dairy, eggs, soy, peanuts, tree nuts, fish and shellfish.  However, a variety of foods can cause this type of reaction.

Symptoms:  Depending on the location symptoms can vary greatly and include nasal congestion, sinusitis, asthma, hives, eczema, nausea, abdominal pain, constipation or diarrhea, swollen joints, racing heart, fatigue, brain fog, among many other symptoms.

Timing:  The T-cell mediated delayed hypersensitivity reaction typically occurs from 12 to 72 hours after exposure to the allergen. Therefore, it is more difficult to diagnose.

Testing:  (we are currently working on this.  Stay tuned.)

Treatment:  From your diet, eliminate foods that contain the allergen.

Number of People Affected:  unknown/unstudied



3.  Gluten Sensitivity

Immune ReactionGluten sensitivity is the "new kid on the block" of gluten-related disorders. The University of Maryland's recent research on the differences between gluten sensitivity and celiac disease shows that gluten sensitivity is triggered by the innate immune system, which is a more primitive and immediate response than the more sophisticated adaptive immune response seen in celiac disease. People with gluten sensitivity do not suffer from the intestinal damage that characterizes celiac disease, although clinical symptoms can be similar.

Causes:  The gluten found in wheat, rye, barley, spelt, and triticale.  Gluten can also be found in foods due to cross contamination or processing.  Gluten can also be found in beauty products, cosmetics, and personal care products.

Symptoms:  Just as in celiac disease, gluten sensitivity can affect all body systems and generate a wide variety of symptoms. Gastrointestinal symptoms can include diarrhea, bloating, cramping, abdominal pain and constipation. Behavioral symptoms can include “foggy mind,” depression and ADHD-like behavior. Other symptoms include anemia, joint pain, osteoporosis, and leg numbness.  There are up to 100 symptoms thought to be associated with gluten sensitivity.

Timing:  (Working on this.  Please stay tuned.)

Testing:  You need to be tested for celiac disease to rule out the possibility of long-term complications. Accordingly, do not go on a gluten-free diet until the possibility of celiac disease has been eliminated through testing. If you go on a gluten-free diet and are then tested for celiac disease, the tests could be falsely negative due to the lack of autoantibodies in your blood serum.This is something to discuss with your family physician or health care provider. Although researchers at the The Center for Celiac Research are working to develop tests for gluten sensitivity, currently there are no definitive blood tests for the condition.

Treatment:  A gluten-free diet.  However, please do not undertake the gluten-free diet as treatment without the supervision of health care professionals as nutritional considerations as well as health considerations must be taken into account with this treatment.

Number of People Affected:  20 million (U.S. alone)

To learn more about gluten sensitivity, please read:  Interview w/ Alessio Fasano Part 3:  Gluten Sensitivity (A "New" Food Allergy)

Auto-Immune Reactions to Food

Celiac Disease

Immune Response:
  Triggered by exposure to gluten, celiac disease is a genetically determined autoimmune disorder that affects approximately one percent of the U.S population. The autoimmune response causes damage to the small intestine resulting in malabsorption of nutrients.

Causes:  The gluten found in wheat, rye, barley, spelt, and triticale.  Gluten can also be found in other foods due to cross contamination or processing.  Gluten can also be found in beauty products, cosmetics, and personal care products.

Symptoms: Symptoms of celiac disease include diarrhea, constipation, weight loss, abdominal pain, chronic fatigue, weakness, malnutrition, and other gastrointestinal problems. In children, the symptoms may include failure to thrive (an inability to grow and put on weight), irritability, an inability to concentrate, diarrhea and bloating. Further, people affected by celiac disease may experience extra-intestinal symptoms that involve many systems and organs including bones (osteoporosis, arthritis, and joint pain), blood (anemia and bleeding), reproductive system (infertility and reoccurring abortion), nervous system (chronic fatigue syndrome, depression, dementia), and behavioral changes.  

Another manifestation of celiac disease is a skin rash called "Dermatitis Herpetiformis" (DH).  A skin biopsy is typically taken to determine if you have this manifestation.

In some cases known as "silent celiac disease," there are no symptoms at all.

Timing:  immediate.

Testing:  Please refer to this article for testing recommendations:  Interview w/ Dr. Alessio Fasano:  How to Get Tested for Celiac Disease.

Treatment:  A gluten-free diet.  However, please do not undertake the gluten-free diet as treatment without the supervision of health care professionals as nutritional considerations as well as health considerations must be taken into account with this treatment.

Number of people affected:  3 million (U.S. alone/1 in 133 people); 1% of global population



Oral Allergy Syndrome (or “Pollen-Food Syndrome”)

The following information on Oral Allergy Syndrome is taken from the Food Allergy & Anaphylaxis (FAAN) website.  More information is in the works from our contributors.  To access the original article from FAAN, please click here.

What Is It?  Oral Allergy Syndrome is a term used to describe itchy or scratchy mouth symptoms caused by raw fruits or vegetables in people who also have hay fever. Symptoms are typically limited to the mouth. This reaction is caused by an allergic response to the pollen that crosses over to similar proteins in the foods. Most people affected by oral allergy syndrome can eat cooked fruits or vegetables because the proteins are sensitive to heating. The condition is also known as pollen-food syndrome.

Immune Reaction:  (working on this, please stay tuned)

Who is affected?  Older children, teens, or young adults; typically patients have been eating the implicated foods without problems for many years.

Causes:  Hay fever is usually present before oral symptoms (seasonal allergy to pollens) to foods begin.  Typical pollen related foods are*:

•    Birch, related to apples, carrots, peaches, plums, cherries, pears, almonds and hazelnuts.
•    Grasses, related to tomatoes
•    Ragweed, related to melons, zucchini, cucumbers, kiwi, bananas

*Not every patient allergic to pollen develops these cross-related food-based symptoms.  Patients may react to a few, all, or none of the foods.

Symptoms:  The symptoms are limited and local.  They include an itchy mouth and throat.  Occasionally the patient will have itchy ears and lip swelling.  Raw fruits or vegetables cause the symptoms.  Patients usually can tolerate cooked or canned foods, as well as juices.
Timing:  Occurs within minutes, and the symptoms are usually resolved just as quickly after the food is swallowed or removed from the mouth.

Testing:  (we are currently working on this.  Stay tuned.)

Treatment:  Typically, treatment is unnecessary.

Non-Immune Reactions to Food

Food Intolerance

Food reactions that do not involve the immune system are commonly called food intolerances. For example, lactose intolerance or adverse reactions to substances in food, such as food additives can be considered food intolerances.

Potential Causes:

•    Can be due to a metabolic disorder such as an enzyme deficiency.
For example, if there is insufficient lactase enzyme in the gut to break down lactose, bacteria in the gut act upon the lactose sugar producing symptoms of flatulence, bloating, abdominal pain and diarrhea.
•    Can be due to the pharmacological properties or natural occurring chemicals in the food.
For example, tyramine in aged cheeses can cause headaches. Or high levels of histamine in certain cheeses, wines, and fish may produce histamine toxicity, which can resemble an allergic reaction to food.

•    Consumption of certain food additives can produce adverse reactions that mimic allergic symptoms. For example, monosodium glutamate (MSG) can cause symptoms such as numbness, headache, flushing and lightheadedness. And tartrazine (yellow dye #5) can cause hives and may trigger an asthmatic attack.

Food Toxicity

Food toxicity can be due to contaminated or spoiled food. The most common food toxicity is food poisoning due to bacteria and toxins released by bacteria.

It can also be due to toxins that occur naturally in foods. For example, potatoes (and other nightshade vegetables) contain toxic compounds known as glycoalkaloids such as solanine. Exposure to light increases the glycoalkaloid content in the potato and eating potatoes with high concentrations of glycoalkaloids can produce gastrointestinal symptoms such as nausea, cramps, vomiting, and diarrhea. In addition it can affect the nervous system causing weakness, dizziness and confusion. Proper breeding and storage of potatoes keeps the glycoalkaloid content low and thus harmless. Cooking at high temperatures also destroys the toxin.


Food Aversion

The food intolerance has a psychological basis. The symptoms may be due to the emotions associated with the food and not the food itself.