Food allergies & intolerances

An allergy occurs when the body’s immune system reacts to a normally harmless substance that it sees as harmful.

Although many substances can cause an allergic reaction (such as insect stings, medicines, dust, pollen and latex gloves), this article will specifically deal with food allergies.

What is a food allergy?

With a food allergy, the body’s immune system overreacts to the protein found in the food (because it thinks that the protein is harmful) and overproduces a group of antibodies called IgE antibodies.  The antibodies cause a reaction process, resulting in the release of histamine and other chemicals into the body.  These chemicals cause the allergic reaction symptoms.

Allergic reaction symptoms range from mild to severe and can include:

  • Skin – hives, swelling, itching, eczema.
  • Gastrointestinal – cramps, reflux, colic, vomiting, diarrhea, swelling and itching of lips/mouth.
  • Respiratory – sneezing, asthma, breathing, cough.
  • Circulation – low blood pressure/dizziness.
  • Anaphylactic – life threatening, can include swelling of airways, drop in blood pressure, difficulty breathing, wheeze or persistent cough.

The reaction usually happens within minutes or up to several hours after ingesting the food.  Even a tiny trace of food can trigger an allergic reaction, and not everyone will react the same way.

The food that causes the allergy is known as an allergen.  The main foods that people are allergic to are eggs, cows milk, peanuts, soy, fish, seafood, wheat and tree nuts.  It is not entirely clear what causes allergies, but we do know that there is a genetic component to developing allergies.   A lot of children who have allergies will lose them as they grow older, but for those who don’t, it tends to be allergies to peanuts, tree nuts and fish that remain.

How are allergies diagnosed?

The first step to diagnosing allergies is to visit a GP, Allergy Specialist or Pediatrician who can undertake a clinical history of past suspected allergic reactions and symptoms.  Tests can then be ordered to help confirm the suspected allergies.  These are:

  • The skin prick test – where small drops of the allergen are placed on the skin (either the forearm or back).  The skin is then pricked to allow a tiny amount of the allergen into the skin, and then the skin is observed for any reactions.  If there is a reaction (i.e. hives), then it is likely that you are allergic to that allergen.
  • Blood test (RAST) – which measure the amount of IgE antibody produced to a specific allergen in the blood.  If there is a high number of antibodies, then it is likely that you are allergic to that allergen.

The results of the tests should always be considered in conjunction with the clinical history of reactions and symptoms, in order to arrive at a diagnosis.

It may also be helpful to keep a food diary (of what is eaten and what reaction occurred) to assist in the diagnosis process.

What is a food intolerance?

A food intolerance is different to an allergy.  It is when the body has an adverse reaction to food that does not involve the immune system.   Instead, the reaction may be caused by a range of things, including a lack of enzymes in the digestive system (that are needed to digest the food) or a toxic response to chemicals found in the food.

The response may be immediate or delayed and is often dose responsive (i.e. eating occasional small amounts of the food may not cause problems).  Common food intolerances are lactose, wheat, food additives and fructose, and symptoms can include bloating, diarrhea, nausea and stomach pain.  The symptoms of food intolerance usually clear by themselves (without requiring urgent medical attention) and are not life threatening.

There are no reliable tests available to diagnose intolerances, and an Elimination/Reintroduction diet is the most useful diagnostic tool.  This should be done in consultation with a Doctor or Dietitian.

A short note on Coeliac disease

Coeliac disease is different again to food allergies and intolerances.  It is a lifelong autoimmune disease.  With Coeliac disease, the body has a permanent intestinal reaction to gluten, where the cells lining the small intestine become damaged and inflamed.  It is a serious condition that should be properly medically diagnosed.  If you have Coeliac disease, you will need to strictly avoid all gluten.

How are food allergies managed?

There is no cure for food allergies – allergies are managed by avoiding the food that you are allergic to.  Accurate diagnosis is therefore important to ensure that you are only avoiding what is necessary and are not needlessly restricting your life or nutritional intake.

If your child has an allergy, it is important to discuss an action plan with your Doctor or Specialist so that if an allergic reaction does occur, you (and other caregivers) know how to manage the reaction and which medications to use.  Some over the counter pharmacy medications may be used to manage mild symptoms, while steroids, breathing medications, immunotherapy or an Epi-Pen (adrenaline auto-injector) may be needed for more severe reactions.  Anaphylactic reactions are life threatening and require urgent medical attention – an Epi-Pen should be available at all times and caregivers should know how to use it.

You will also need to plan ahead for social occasions, eating at restaurants, travelling away from home and for schooling.  Teaching your child about their allergy and how to manage it (as is age appropriate) is also important, along with educating other caregivers or extended family members.  Things to consider include:

  • Reading all food labels to check the ingredients.
  • Avoiding any food, cutlery or kitchen utensils that may have been cross contaminated with the allergen.
  • When eating away from home, clarifying with the hosts or restaurant staff the ingredients used in meals and asking about the risk of any cross contamination.
  • Taking your own food out with you if necessary i.e. snacks for playdates or allergy friendly alternatives for the Saturday morning after sport treat.
  • Ensuring safety at school – for example, consider whether all staff (including relievers and duty teachers) know of the allergies, education of classmates, shared food (i.e. lunches, birthdays and other special occasion treats), cooking or other food use in lessons, school trips, access to medication at school.

These ideas would also be applicable if your child has food intolerances (depending on the severity of their symptoms) or Coeliac disease.

For further information on food allergies or intolerances, please contact Parent to Parent to request a personalised information pack.


Lisa Piriri square v
Lisa Pirihi
Project Coordinator for Parent to Parent
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