A food allergy is an abnormal reaction to a food by the immune system that can cause unpleasant and in some cases, life threatening symptoms.

What is a food allergy?

With the growing prevalence of dietary restrictions, you may be wondering what is a food allergy and why are they so common. You may be sceptical, thinking these dietary restrictions are less about a medical reason and more about personal preference. And who would blame you? Back when I was a child, food allergies were virtually non-existent.

In this series of articles, I will answer the question 'what is a food allergy?', discuss why there is a rise and talk about how food allergies can be prevented.

So, let's start with the definition of an allergy. An allergy, whether it’s from food, animal dander or insects, occurs when there is an immune response. The response can happen after the child has come into close contact or ingested the allergen.

The immune system is designed to protect our bodies from harmful pathogens, infections and other environmental dangers or foreign substances.

But it the case of a food allergy, the immune system views the food as a threat. There are several kinds of food allergy reactions which have been divided into two main categories: IgE and a non-IgE mediated response.

IgE mediated response

This is the most common type of food allergy reaction and is caused by IgE allergy antibodies in food. The symptomatic response will be quick, occurring within a few minutes to an hour after the child has been exposed to the food. This type of food allergy is typically easy to diagnosis with a skin prick test or an allergy blood test.

Non-IgE mediated response

The reaction of a non-IgE mediated food allergy is delayed with symptoms occurring hours or even days after the exposure to the food. This food allergy is less understood and more difficult to diagnosis than an IgE mediated allergy. As a result, many individuals suffer for sometime before the allergen is identified. Diagnosing a non-IgE mediated food allergy usually requires a food elimination and challenge protocol that can be carried out under the guidance of your health professional.

What is an allergen?

Allergen is a term for anything that causes an allergic reaction. This is the trigger that the immune system is singling out as a threat to the body. In the case of food allergies, the allergen is typically a protein in the food. According to the Australasian Society of Clinical Immunology and Allergy, the most common food allergens causing 90% of reactions include:

Egg
Cow’s milk
Peanut
Tree nuts
Sesame
Seafood
Fish
Soy
Wheat

It’s important to remember that the allergen itself is not necessarily the cause of the food allergy. Instead, it appears they are simply the target of the immune system’s response. We’ve had many of these common allergenic foods in our diets for thousands of years, yet it was only in recent years food allergies have appeared, especially at such a high prevalence. With this in mind, it is easy to understand why the medical community has stopped recommending children avoid common high allergenic foods in an attempt to prevent food allergies from occurring. Instead, early exposure to these foods could see a reduction in the risk of developing a food allergy.

What are the symptoms of a food allergy?

In children with a food allergy, their immune systems attack the protein in the particular food which it sees as a threat. The allergic response to the protein causes inflammation which can be mild or exoculate into a serious reaction such as anaphylactic shock. The signs and symptoms of a food allergy typically depend on where the reaction occurs in the body.

As an allergic reaction is in response to a factor outside of the body, the areas of the body that are affected by the allergen are typically the gut, skin or airways. With food reactions, we commonly see the response occurring on the skin presenting as redness, eczema

or hives, or in the gut with the individual experiencing symptoms like vomiting or diarrhoea. However, there can be a wide variety of signs and symptoms of a food allergy reaction.

Symptoms of a food allergy can include:

Swelling of lips, eyes or the entire face
Hives or skin rash
Abdominal pain, diarrhoea or vomiting
Reflux
Colic
Difficulty breathing
A persistent cough or wheeze
Swelling of the throat or tongue
Change in voice
Dizziness, pallor or floppy presentation
Failure to thrive

What age does a food allergy develop?

An individual can develop a food allergy at any age. Food allergies are most common in infants and children less than 5 years old. Some children can “grow out” of the food allergy depending on the allergen. Most peanut, tree nut, sesame and seafood allergies tend to be lifelong. Therefore learning to prevent and manage food allergies in children has become a priority of many health professionals and parents.