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The Difference Between a Food Allergy and Food Intolerance

Sep 2, 2020
Jan 27, 2021
4 minutes
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Medically reviewed by

Everyone reacts differently to food. Some reactions can be more severe than others. Many people can’t piece the puzzle together and can’t quite tell if they are experiencing an allergic reaction to food or if they have a food intolerance. Do you know that there is a difference between the two? Food allergies and food intolerances have many similarities, but there are distinct differences, even though they are often confused with each other.

Let’s look at each of them in more details.

Food Allergy

A food allergy can be defined by the activation of antibodies to specific foods that cause the body to react in different ways ranging from mild to very serious reactions.


Symptoms of a food allergic reaction include:

  • Itchy, uncomfortable feeling
  • A red, itchy rash
  • Swollen tongue, throat, lips, roof of mouth and general face swelling
  • Possible vomiting


Food allergies can develop at birth or arise in adulthood. Scientists do not currently agree on how an allergy starts and why.  

The cause of a food allergy comes from a weakened immune system where the body mistakes a food protein for an infectious threat.

Anyone can be affected by a food allergy.  Allergies are not specific to certain types of foods. The negative reaction can occur in relation to any number of foods you consume on a regular basis.

Foods such as dairy (milk/eggs), nuts, fish, or specific fruits and vegetables are among the most common ones that cause an allergic reaction.

Types of Food Allergies

  1. Immunoglobulin E (IgE) mediated: The body’s immune system will begin producing antibodies called IgE. This type of allergy can risk anaphylaxis (aka the allergic reaction), that can begin within minutes of food consumption.
  1. Non-IgE mediated: The body’s immune system will react, but the IgE antibodies are not involved in this type of allergic reaction.
  1. Mixed IgE and non-IgE-mediated: People may experience a mixture of both types of reactions.


There are several methods to treating a food allergy. Usually, the first step is to speak with your health specialist about an allergy test. This will help recognize your condition early before another reaction can occur.

Don’t make sudden changes in your diet that completely eliminate specific foods. Always speak to a dietitian before making the decision to cut foods out of your diet.

Typically, those who suffer from food allergic reactions are provided with an injector pen filled with doses of adrenaline.

Food Intolerance

Food intolerance is the opposite of a food allergy; the reaction is caused by food products that are non-proteins. Food intolerances are actually more common than food allergies. Food intolerance causes the body to have difficulty digesting specific foods.


Symptoms of food intolerance include:

  • Headaches/migraines
  • Runny nose
  • Bloating
  • Irritable bowels
  • Stomach aches
  • A general feeling of being unwell

The main difference between the symptoms is that with food allergies, even a small intake of food will cause a reaction. On the other hand, if you are intolerant to specific foods, you won’t see any visible signs right away after you eat; larger amounts of the questionable food are needed before a reaction ensues. Symptoms of food intolerance take much longer to develop. One may not realize that there is a problem for a long period of time.


There are several causes of food intolerance. The most common factor is the absence of enzymes needed to digest foods which in turn will cause improper digestion. Almost all foods require enzymes to break them down. With a lack of appropriate enzymes, the digestive tract will be unable to break down foods and cause bowel irritation (i.e., gas, bloating, diarrhea, headaches).

Other than foods, some drinks containing certain chemicals (especially drinks high in caffeine) may trigger an adverse reaction.

Food poisoning can also be a culprit. The toxicity of chemicals in foods that are not cooked properly can cause a physical reaction in your body (e.g., nausea, vomiting, diarrhea).

Even histamine, found in foods like fish if not properly stored, can spark a bad reaction in highly sensitive people.  

Types of Food Intolerance

  1. Gluten
  2. Wheat
  3. Lactose
  4. Caffeine
  5. Additives

A common intolerance is with gluten. Some reactions can come from eating something as simple as bread. Other foods high in gluten include:

  • Beer
  • Bread
  • Pasta
  • Cakes and cookies

For more information on this topic, feel free to read our article on: “Celiac Disease: Symptoms, Causes, Treatment & Screening (How to Get Tested)

There are a few important differences between a food allergy and food intolerance you should be aware of:

  • Food intolerance cannot be life-threatening; a food allergy might be.
  • Food intolerance will cause some irritable pain in the abdominal area but will not cause severe reactions such anaphylaxis .
  • The amount of food digested can affect whether you are experiencing a food intolerance or food allergy. The reaction will happen quickly with an allergy.
  • There is no test to determine if one suffers from food intolerance. However, food allergy tests are available and can provide accurate results.
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