Food Allergies and Intolerances

Category: Food Allergy and Intolerance
Food Allergy and Intolerance


What is a Food Allergy?

Food allergy occurs when the immune system responds to a food that the body incorrectly recognises as harmful. Antibodies are produced as part of this response and a complex chain of events occur, leading to the release of substances such as histamine.
This histamine release causes the symptoms of allergy including lip, eye and face swelling, nettle-sting-type rash or hives, vomiting or tummy pains. In its  most severe form, allergy can cause life-threatening anaphylaxis (pronounced anna-fill-axis).
An allergic response to food always involves the immune system. Symptoms are frequently seen within minutes but can be delayed up to 72 hours after eating the food involved.

In Ireland, statistics show that approximately 5% of children and  3% of adults actually suffer from food allergies.

How is Food Allergy Diagnosed?

The story trumps everything! An allergy-focused history and examination by a qualified health care professional is the best starting point. They will recommend what test, if any is needed. Allergy tests only give a measure of sensitivity to a food, not allergy to that food.
Testing should focus on either or both:

1) Skin prick tests
2) Measuring the level of Specific IgE antibodies in the blood. This test replaces ‘RAST’ which is now obsolete.

These two tests have been studied, validated and are evidence-based measures of allergic sensitisation.
Some specialist centres may perform allergen provocation tests where the suspected allergenic food is given to the patient under medical supervision. This may be risky for people who have a severe food allergy and is therefore carried out in a in a hospital setting with full resuscitation equipment.

Common Food Allergens:

Cow's milk
Other nut

These eight allergens account for about 90% of all allergic reactions, however allergic reaction to newer allergens such as sesame and kiwi are becoming more common.

What is a Food Intolerance or Non-Allergic Food Hypersensitivity?

An intolerance to food is rarely life threatening and tends to occur hours or days after the food is eaten. The symptoms are generally described as an unpleasant reaction to a particular food involving for example, tummy cramp, flatulence, vomiting and diarrhoea.

How is a Food Intolerance diagnosed?
Your trained health care professional / GP/ doctor should do a physical examination and take a detailed history including diet, symptoms involved and suspected triggers. A family history of intolerances is known to be a significant risk factor.

What is a Food Aversion?

A food aversion is a psychological aversion to a particular food or foods. It can result in physical symptoms similar to those of a food intolerance. However, if you are unaware that you have eaten the food, there are no symptoms.

What is the role of the dietitian in the diagnosis and management of food allergies?

Dietitians are uniquely placed to support those affected by food allergy by:
1. Providing tailored education to those affected by food allergy
2. Being a member of the allergy team
3. Identifying and recognising common sources of food allergens
4. Devising safe, nutritious elimination diets
5. Identifying key nutrients and their food sources required for each stage of life.
6. Recommending foods for special medical purposes and food supplements where appropriate.

Help and Advice

If you suspect that you have a food allergy or intolerance, seek advice from your GP.  You may then be referred onto an allergy specialist. 
Visit the Irish Food Allergy Network for further information including how to access a dietitian. If you would like to visit a private dietitian for a consultation please visit to search for an experienced dietitian in your area.

**Are you a Dietitian?: For updated information ......please refer to the free HSELand e-learning module 'Recognising and managing Food Allergy in the Community. You will have access to the 'Nutrition reference pack for Children 0-1 years' which reflects current research and evidence for the diagnosis, management, treatment and prevention of food allergy.   March 2022