ausEE Inc.

a charity dedicated to improving lives affected by eosinophilic disorders

What is Allergy?

Allergy occurs when a person's immune system reacts to substances in the environment that are harmless for most people. These substances are known as allergens and are found in house dust mites, pets, pollen, insects, moulds, foods and some medicines.


Atopy is the genetic (inherited) tendency to develop allergic diseases. People with atopy are said to be atopic. When atopic people are exposed to allergens they can develop an immune reaction that leads to allergic inflammation (redness and swelling).


This can then cause symptoms in the:

  • nose and/or eyes - hay fever (allergic rhinitis/conjunctivitis)
  • skin - eczema, hives (urticaria)
  • lungs - asthma


A substance that is an allergen for one person may not be for another - everyone reacts differently. The likelihood (or risk) of developing allergies is increased if other family members suffer from allergy or asthma.


What happens when you have an allergic reaction?


When a person who is allergic to a particular allergen comes into contact with it, an allergic reaction occurs. This begins when the allergen (for example, pollen) enters the body, triggering an antibody response. The antibodies attach themselves to special cells, called mast cells. When the pollen comes into contact with the antibodies, the mast cells respond by releasing certain substances, one of which is called histamine. When the release of histamine is due to an allergen, the resulting swelling and inflammation is extremely irritating and uncomfortable.


Which areas of the body may be affected?


Depending on the allergen and where it enters your body, you may experience different symptoms. For example, pollen, when breathed in through the nose, usually causes symptoms in the nose, eyes, sinuses and throat (allergic rhinitis). Allergy to foods usually causes stomach or bowel problems, and may cause hives (urticaria). Allergic reactions can also involve several parts of the body at the same time.


Life threatening allergic reactions require immediate treatment.


Most allergic reactions are mild to moderate, and do not cause major problems, even though for many people they may be a source of extreme irritation and discomfort. However, a small number of people may experience a severe allergic reaction called anaphylaxis. It is a serious condition which requires immediate lifesaving medication. Some of the more frequent allergens which may cause this are peanuts, shellfish, insect stings and drugs. If you know that you have a very severe allergy, you should have an Anaphylaxis Management Plan from your doctor, which should include an ASCIA Action Plan for Anaphylaxis.


This information has been sourced from The Australasian Society of Clinical Immunology and Allergy (ASCIA); for more information and additional resources please visit their website http://www.allergy.org.au/.


Allergy Testing

After an EGID diagnosis is confirmed, it is typically recommended for allergy testing to be carried out by an allergist or trained and experienced medical practitioner. Skin prick testing is the most common form of allergy testing.


  • Skin prick testing or scratch test is where a diluted extract of the food/allergen is placed on the skin of the forearm. This portion of the skin is then pricked/scratched with a needle and observed for swelling or redness. A positive scratch test indicates that the patient has the 'IgE' mediated response that is specific for the food/allergen being tested. The severity of the response is based on the size of the swelling “wheal”.

  • Atopy patch testing looks at “delayed” or ‘non-IgE’ mediated reactions. Small amounts of pure food are placed onto small discs which are then taped to the back. The patches are removed after 48 hours and the results are read at 72 hours. Positive results include induration or papules reactions.

  • RAST testing measures the presence of food-specific IgE antibodies in the blood of patients, blood is drawn and sent to a lab for testing to determine “predictive values” for certain foods. RAST testing may not be as helpful for identifying foods that cause EGID reactions.


It is advised that the patient should not be taking antihistamines or oral steroids for 48 hours before undergoing skin prick or atopy patch testing.


In EGID patients it is not uncommon for allergy test results to be negative. This means that a food can be consumed with no obvious reaction to it, but over a period of days to weeks the eosinophils triggered by the food can cause inflammation to the esophagus. In these instances it is useful to keep a Food Diary to assist in identifying the offending food.

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Page last modified: 9 October, 2016