Food Allergies and Intolerances

A food allergy is much more dangerous than having an intolerance. But do you know the difference between the two?
Food Allergies and Intolerances

Last update: 06 February, 2020

When talking about adverse reactions to food, allergies and food intolerances come up. Both produce annoying symptoms and adverse health effects, but they aren’t the same.

Definitions of food allergies and intolerances

A food allergy or hypersensitivity is an adverse reaction spurred by the immune system against a certain food, usually a food protein. The cause of the symptoms comes from a person’s response to food—not the food itself. Additionally, an individual’s allergy symptoms can be very different from those of another person, even when it comes to the same foods.

On the other hand, food intolerance is an adverse reaction to a food in which the immune system doesn’t participate. Intolerances happen because of the way your body processes the food or its components.

This condition arises from a toxic, pharmacological, metabolic, digestive, psychological, or idiopathic reaction to a food or one of the chemicals it contains.

The term “food sensitivity” is a wild card. People often use it as a synonym for both food allergy or intolerance, but it doesn’t indicate the cause of the symptoms.

The individual’s response to a food or food component, as well as the body’s interpretations of it as either “friend” or “enemy”, is conditioned by multiple factors. These include:

  • Genetics.
  • Intestinal barrier health.
  • Intestinal microflora
  • Stress.
  • Environmental and physiological elements.
  • Psychological factors.

Allergy incidence

Any food can cause an allergic reaction, but only a few items are the main culprits:

  • Dairy and eggs are the foods that most often cause early childhood allergies in all western countries. Of these two, egg allergies are more persistent.
Egg replacements

  • Allergies to milk, soy, egg, and wheat often spontaneously disappear in children. However, allergies to nuts, fish, and shellfish are often more persistent.
  • Foods that most often produce allergies in older children, adolescents, and adults include nuts and dried and fresh fruit (apples, peaches, kiwis, for example). 

Food allergies and intolerances: diagnostic testing

The diagnostic approach begins with the patient’s medical history and a physical examination. This also goes together with an allergological study, which consists of:

Patch tests

Patch tests consist of observing the reaction of a patch of skin that’s in contact with the allergen. The doctor will either prick the skin with commercial extracts or cover it with small chambers or discs filled with test substances. Positive results indicate the possibility of an allergy. If the result is negative, then an allergic response can be ruled out.

Currently, there’s only one patch test that serves as a definite diagnostic for cases of anaphylaxis, which happens after ingesting an isolated food. In other words, the test is positive when you’ve had a respiratory reaction when eating said food.

Pathogenic diagnosis

With this method, a doctor performs an analysis and requests specific IgE antibodies. If the test is positive for the IgE antibody of a specific food, then the doctor will order more tests to confirm the allergy. The detection of IgE antibodies against food implies sensitization, but not necessarily a clinical allergy.

Oral tolerance test

Oral provocation is the most reliable method for diagnosing an allergy. For this, the subject is exposed to the food suspected of causing an allergy and is monitored for a reaction. This procedure can be done in different ways.

First, if the subject ingests the food he/she has an allergy to, it’s an open oral tolerance test. This type of test is for doubtful cases where the patients avoid suspicious food as well as for young children. If the results are still dubious, a double-blind confirmation is needed.

The simple placebo-controlled blind test is carried out with two options: one contains the suspected allergen and the other does not, but only the examiner knows which is which. This technique serves to eliminate the patient’s bias since allergic people can be easily suggestible. This test is particularly useful in cases with subjective symptoms. It’s the test to take when the double-blind tests aren’t accessible.

Lactose intolerant

The third option is a double-blind, placebo-controlled oral tolerance test. You need three people to perform this test: the doctor, the patient, and a third person who decides whether the sample carries the allergen or not.

This is the diagnostic reference pattern since it eliminates the bias of the patient and the doctor. This is important to do if an objective diagnosis is necessary.

Diagnosis of intolerance

The first thing to do is to identify which ingredient causes a reaction. Once it’s identified, it’s important to quantify the amount that actually generates symptoms. For example, in the case of suspecting a lactose intolerance, it’s important to measure exactly how much milk is ingested without symptomatology.

An exhaled hydrogen test is done to confirm that there’s poor absorption of carbohydrates. Doctors administer this test in cases of fructose, lactose, or galactose intolerances. In order to find out the dose that causes symptoms, an oral provocation test can be performed. Doctors can perform any of the modalities as well, including the open, single-blind, or double-blind tests.

Treatment for food allergies and intolerances

The basis of allergy treatment is avoiding triggering foods, but you have to keep in mind that it isn’t always possible. This means that instructions for emergency treatment must be provided. This will likely consist of administering adrenaline to the allergic person in case of an attack.

Reading food labels carefully is essential as well, as allergic reactions can be triggered even by trace amounts of the allergen. There’s a mandatory allergen list on every label, and it includes the following:

  • Gluten.
  • Shellfish.
  • Eggs.
  • Fish.
  • Peanuts.
  • Soy.
  • Dairy.
  • Nuts.
  • Celery.
  • Mustard.
  • Sesame seeds.
Allergies to nuts and seeds

  • Sulfur dioxide and sulfites.
  • Mollusks.
  • Lupins.

Avoidance diets, along with rescue medication, don’t cure food allergies. Oral immunotherapy emerged from this, however.

Oral immunotherapy tries to induce tolerance by oral administration of the allergenic food. It begins with intaking very small amounts and progressively increasing the doses until reaching a normal ration. A patient must consume the allergen on a daily basis for a sustained period of time.

This treatment applies to cases in which there are persistent allergies to an essential or basic food in a person’s diet or a severe allergy to a food that’s difficult to avoid in normal diets.

To sum it all up, food allergies and intolerances are perfectly treatable problems. Of course, it’s of primordial importance to identify the symptoms, make a proper diagnosis, and take early measures for avoiding serious symptoms.

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Allergies are some of the biggest nuisances you can experience in your day-to-day life. Here are a few common types of allergies you should know about.

  • Salas-Salvadó, J., i Sanjaume, A. B., Casañas, R. T., i Solà, M. E. S., & Peláez, R. B. (Eds.). (2019). Nutrición y dietética clínica. Elsevier Health Sciences.
  • Bebidas, F. E. de I. de la A. y. (2013). Alergias e Intoleracias Alimentarias. Guía de Gestión de Alérgenos En La Industria Alimentaria, 36–86.