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Allergies - causes, symptoms, treatments

Author Philippa Murphy

Allergies - causes, symptoms, treatments

There is so much talk about allergies these days and much confusion. It seems many of the newborns that I see in my clinic have been labelled with an allergy when in actual fact they have a food intolerance. So I’d like to take some time to clarify the differences of these and delve into some factual information about causes, symptoms and treatment. First though, let’s look at the prevalence of allergies in our world.

Allergy UK estimate that 30-40% of people have an allergy at some stage in their lives and that 50% of children are diagnosed with an allergic condition. However, many state that it is difficult to place a specific percentage on allergy population figures.

It is currently thought there is a rise of allergies in our country but, according to the Allergy Auckland Clinic, ‘there are also those that claim, “the food allergy epidemic is due to inconsistencies in the diagnosis of food allergy and the definition of the cases and defects in the methods of the studies” and there is some truth to all of the criticisms.’ 1

Researchers recently collated 900 published studies in hope of finding the percentage of people with food allergy. They found that the number of people that thought they had an allergy ranged from 3-38%, a big range. However only 1-11% of these people had medical confirmation of the allergy. They concluded there is a large gap between confirmed diagnosis and self-diagnosed allergy. Most of the clinically proven studies they looked at reported that 1-5% of the total population had a good allergy.2 In New Zealand the prevalence studies on food allergy have been limited.3

Difference between food allergy and intolerance

Quite simply, while some of the symptoms are similar it is the timing and dose response that defines an allergy compared to an intolerance. A food allergy causes an immune system reaction, affecting many organs in the body, causing a range of symptoms which I have detailed below. Food intolerances have symptoms that are generally less serious and often limited to digestive issues like bloating, gas, cramps, to name a few. Research shows us that a large number of children grow out of early intolerances by five years of age.

What is an allergy?

Allergies are caused by a hypersensitive immune response to substances that either enter or come in contact with the body. This substance is called an ‘allergen’ which can be a food, drink or something within the environment.

What happens with an allergy is that the immune system reacts as though the allergen is a harmful bacteria, virus, toxin or fungus that can cause a disease. This has it releasing immunoglobulin E (IgE), which is a type of antibody that destroys the allergen. It creates chemicals to do this and it is these chemicals that cause the allergic reaction e.g. histamine, one of the chemicals causes muscles to restrict, including airways and blood vessels, along with making the nose produce more mucus. So it is not the food that produces the allergic reaction but the person’s immune system that mistakes particular harmless substances for harmful ones.

Common symptoms 4

  • Sneezing, runny blocked nose and or itchy nose
  • Itchy, red, watery eyes
  • Wheezing, chest tightness, shortness of breath
  • Swollen lips, tongue, eyes or face
  • Tummy pain, feeling sick, vomiting or diarrhoea
  • Hives

Severe allergic reaction symptoms 5

In rare cases, an allergy can lead to anaphylaxis which can be life-threatening. Anaphylaxis effects the whole body and usually develops within minutes to half an hour. This is a medical emergency that require immediate treatment so do call the ambulance. Symptoms include…

  • Weak pulse, pale or blue colouring of skin
  • Dizziness or feeling faint
  • Swelling of throat and mouth
  • Difficulty breathing
  • Collapsing, losing consciousness

Diagnosis of an allergy

Your history and symptoms will be assessed and you will either be given a skin prick or blood test to determine if a food allergy is the cause of the symptoms. However, the ‘gold standard’ test is a ‘double-blind placebo-controlled food challenge’ but these aren’t used that much in New Zealand.



Last Updated: 14 November 2016