Difference between food allergy and food intolerance

The precise distinction between food intolerance and a food allergy is often missed.

A food allergy is an adverse immune reaction to a specific food resulting in the production of antibodies (IgE). Any time the food culprit is ingested or comes into contact with the skin, the body releases histamine and causes allergy symptoms like rashes, swelling, diarrhea and vomiting. In the most severe cases symptoms such as swelling of the lips, tongue or face, shortness of breath, breathing difficulties and loss of consciousness can occur.

Food intolerance or food sensitivity is associated with chronic, long term symptoms rather than drastic attacks or anaphylactic shock. People with food intolerance might not even notice that they are having a reaction and this delayed onset of symptoms can take as long as three days to appear after eating a 'trigger food'. Some people who feel continuously unwell may actually be experiencing food sensitivity to foods like dairy, gluten, nuts or eggs.

The terms food allergy, food intolerance, food sensitivity, hypersensitivity are often used interchangeably, and are often confused, but essentially they all mean an abnormal reaction to certain foods which can manifest themselves in a number of ways.

Scientifically, the reactions can be differentiated by the fact that some cause an immune response, whereas others do not.

Reactions producing an Immune Response

The reactions that trigger an immune response are most often referred to as allergies. The most common ones are
classed as follows:
• Type I (IgE reaction)
This is also known as an IgE mediated allergy, Type I hypersensitivity reaction, 'true' or 'classical' allergy. Such a food allergy produces an immediate adverse reaction; i.e. within seconds or minutes after ingestion of certain foods (for example peanuts and shellfish) and produces symptoms such as rashes, sneezing, difficulty in breathing, and for some people can even be life threatening because of an anaphylactic shock. It is usually obvious which foods are responsible for a food allergy and these have to be avoided for the rest of your life.

• Type III (IgG reaction)
This is also known as IgG mediated reaction, Type III allergy, delayed onset, hypersensitivity/food sensitivity, however it is more commonly referred to as food intolerance. This is the type of reaction that is measured in your Food Intolerance Test.
Food intolerances are associated with a range of symptoms that are caused by chronic inflammatory processes. The onset of symptoms is within hours or days after ingestion of the food. Symptoms include anxiety, depression, IBS, headaches/ migraines, fatigue, hypertension, eczema, hypothyroidism, asthma, joint paint, chronic rhinitis, arthritis, weight problems and ðbromyalgia.
The good news is that with a food intolerance, it is possible to eliminate the food from the diet for a period of time and then to re-introduce them gradually back into the diet after an improvement in symptoms.

Reactions that do not produce an Immune Response

Those reactions that do not produce an immune response are most often referred to as intolerances. An example of this type of reaction is an enzyme deficiency such as :
• Lactose intolerance which is due to a deficiency of the enzyme lactase. Symptoms include bloating, excessive wind, diarrhoea and stomach pains.
• Histamine intolerance which is due to the deficiency or inhibition of the enzyme diamine oxidase, DAO. Symptoms include migraines, headaches, dizziness, bowel/ stomach problems, rhinitis, depression, irritation or reddening of the skin. Foods containing histamine include red wine, cheese, tuna fish or chocolate and citrus fruits.