Food Allergies and Intolerances

Food allergies and intolerances are on the rise. If you’re the parent or grandparent of a school-aged child then you know well the many dietary restrictions schools impose to safeguard their students from severe allergic food reactions. No more peanut butter and jelly sandwiches! However, children aren’t the only ones suffering from increased rates of food allergies, adults are too. And when you toss in food intolerances, well, let’s just say it’s tough to throw a dinner party theses days!


It’s important to note the difference between food allergies and food intolerances before we begin. Allergies are caused when a food induces an immune response specific to the allergic pathway. This is referred to as the IgE-mediated allergic response. Food intolerances occur when the body reacts without a direct immune response. However, intolerance reactions can be associated with elevated levels of chronic inflammation over time. True food allergies can bring on anaphylaxis reactions that are life-threatening and require immediate medical attention. In contrast, food intolerances typically impact health over time.

Food Allergy Types

The most common type of food allergy is the immediate-type reaction. Other, less common food allergies can have a delayed onset, but these reactions are rare. The immediate-type, IgE-mediated reaction is divided into two classes, class 1 and 2.

Class 1 Reactions

Class 1 allergies develop in childhood. The most common foods, accounting for 90% of reactions, include cow’s milk, hen’s eggs, legumes (peanuts and soybeans), fish, shellfish, and wheat. The reaction to these foods isn’t limited to the gut but can also affect the skin and airways. Most children will outgrow theses allergies with the exception of peanuts and fish.

Class 2 Reactions

Class 2 food allergies develop in adolescents and adults. They are the result of a cross reactivity in individuals with established respiratory allergies (ie. hayfever) to pollens like birch, mugwort, alder, ragweed, grasses and others. The immune response recognizing the pollen also recognizes certain foods as being similar to the pollen and mounts an allergic response. This is referred to as Oral Allergy Syndrome (OAS).

Oral Allergy Syndrome (OAS)

OAS is the most common type of food allergy experienced by adults. It happens as the result of pollen allergies. An allergic response to pollen can sensitize an individual to developing an allergic reaction to certain foods. For example, allergy to ragweed can cause food allergies to banana, melons, squash, peppers and sunflower seeds among others. You can get a more complete list of common pollen allergies and their associated food allergies here: Get the OAS List

OAS can be seasonal, typical of pollen allergies, with food allergies resolving when the pollen abates. Most of the OAS related food allergies are isolated to the mouth and throat but a few can cause digestive tract upsets.

Food Intolerances

Often mistakenly lumped together with food allergy, food intolerances represent a distinct set of food sensitivities. They are more common than true food allergies and more diverse in their causes. Food intolerances are often associated with chronic inflammatory bowl diseases.

Food intolerances can be brought on by several factors but perhaps the most common is by an enzyme deficiency. Digestion and subsequent food processing of the foods we eat into small chunks of nutrition that the body can use is the job of digestive enzymes. These enzymes are very specific and only affect certain components of the foods we eat. Probably the most familiar example of a food intolerance that involves a digestion enzyme deficiency is the milk-lactose intolerance. Lactose is the naturally occurring sugar found in cow’s milk. It requires a specific enzyme, lactase, to breakdown the lactose sugar into useable nutrition for the body. Other enzyme deficiency food intolerances include those to other sugars, including fructose, maltose, sucrose and sorbitol, histamines that naturally occur in foods, and alcohol. Gluten (a protein found in some grains like wheat) intolerance can also cause Celiac’s disease, an autoimmune disorder.

Beside enzyme deficiencies, food intolerances can be caused by food additives and naturally occurring food chemicals. Some examples of these include:

  • salicylates
  • sulfites (present in wine and medications),
  • sodium glutamate (flavor enhancer),
  • colorants and preservatives (such as tartrazine, benzoates, sorbates etc.),
  • sweeteners (aspartame)¹

Unfortunately, the data on these forms of food intolerances is sparse.

Diagnosis and Treatment

If you suspect that you have a food allergy or intolerance you should speak with your physician. This is not an area of your health that you want to self-diagnose. The process is complex and requires patience but it is important to pursue in order to prevent worsening of the symptoms and damage to organs and tissues.

Starting with food allergy testing may be the easiest route for most. If you know that you have seasonal, pollen allergies then you may already know what pollen you are allergic to clueing you and your doctor into certain pollen-related food allergies. Skin prick testing can be done for both pollen allergies and specific food allergies. These types of tests cannot, however, be used to diagnose food intolerances.

Testing for food intolerances is more complicated and diagnosis usually results when patients have other, secondary conditions that bring them to their physicians such as migraines, chronic inflammatory bowel diseases, chronic pancreatitis, irritable bowel syndrome, eosinophilic gastroenteritis (a form of acid reflux), systemic mastocytosis (an immune cell disorder), celiac disease (caused by gluten), and microscopic colitis.¹ Tests conducted for food intolerances can include blood and stool tests, endoscopy, tissue samples (histology) and breathe tests.

Treating either a food allergy or intolerance requires the obvious, avoiding the foods that trigger the allergy or intolerance. However, it is often difficult to pinpoint exactly what foods are the cause. As I mentioned earlier, OAS is associated with pollen allergies and these can be seasonal, causing the food associated allergies to come and go. Additionally, since food intolerances are more difficult to test for, an individual may never know exactly what food triggers the reaction. Elimination diets can be helpful when a direct diagnosis cannot be made but are also difficult to adhere to and require long periods of time to determine specific allergies or intolerances. Elimination diets are best done under the care of your physician.

If a specific food or food group can be identified as the culprit for either an allergy or intolerance then a diet that avoids these foods is essential. Along with the supervision of your doctor, a registered dietician can help guide and ensure that the modified diet is not missing key nutrients.

For many, however, food allergies and intolerances can be only a minor inconvenience, lacking the heath and life-threatening affects of more serious food reactions.

Until next time, stay well!

Dr. Tobi Schmidt

  1. The Differential Diagnosis of Food Intolerances 10.3238/arztebl.2009.0359

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