Allergy

What is allergy?

Allergy is extremely common, affecting about 20% of Australians at some point in their lives.

During allergic reactions the body’s immune system overreacts in a harmful way to a normally harmless protein (allergen) such as a pollen or a protein in food. The body produces a specific antibody (IgE) against the allergen and when the patient is exposed again there is the release of chemicals including histamine. These chemicals cause the variety of allergic reaction symptoms with itch, sneeze, wheeze, rash and, at worst, anaphylaxis.

Allergic diseases include:

  • Food allergy
  • Hay fever (allergic rhinitis/ rhino-conjunctivitis)
  • Atopic asthma
  • Urticaria (hives)
  • Anaphylaxis
  • Atopic eczema

Reactions typically occur within seconds to an hour of exposure to the allergen and are reproducible; however they occur every time the person is exposed to the allergen. Reactions can vary in severity from mild to severe and potentially life threatening.

Children can be allergic to:

  • Foods
  • Inhalants (especially pollens, house dust mite and animals)
  • Insect stings and tic bites
  • Medicines
  • Moulds
Testing for allergy

Doctors use a combination of the specific clinical history of reactions plus tests such as skin prick tests and blood tests to accurately diagnose IgE mediated allergy. None of our testing methods are 100% accurate and it is important that test results are interpreted in the context of each individual patient’s circumstances.

Skin Prick Tests

The Australian Society of Clinical Immunology and Allergy (ASCIA) recommend skin prick testing as the primary method for diagnosing IgE mediated allergies. Advantages to skin prick testing include its safety, reliability, reproducibility and the generation or rapid results that can be immediately discussed with the patient and their family.

The tests are usually well tolerated by patients including children. False positive and negative results are possible so it is essential that test results are interpreted by a well trained medical practitioner. In some instances, skin prick testing will not be appropriate. In this case your doctor may order specific IgE blood tests to help confirm a diagnosis of allergy.

There are many types of reaction to food. Not all of them are IgE mediated allergy and as such not all can be diagnosed using skin prick testing. Your doctor will help you understand the difference.

Skin prick testing is also not useful for:

  • Non-specific rashes
  • Chronic, idiopathic urticaria
  • Food intolerances
  • Other illnesses that are not mediated by IgE antibodies.
What to expect from Skin Prick Testing

Skin prick testing is performed either on the patient’s forearm or upper back. A drop of specific extract will be placed on the skin and a sterile lancet will make a gentle prick through the droplet, allowing a small amount of allergen to enter the skin superficially.

Patients who are allergic to that extract will develop an itchy red lump (hive) with in 15-20 minutes. This usually resolves within 1-2 hours. At MCPC, testing is available for food and inhalant allergens.

Essential preparation for your skin prick test

There are certain medications that interfere with skin prick tests and must be avoided in the lead up to your appointment.

These include:

Antihistamines – avoid for five days prior to appointment. E.g. Aerius (desloratadine), Claratyne (Loratadine), Polaramine (Dexchlorpheniramine), Phenergan (Promethazine), Telfast (fexofenadine), Zyrtec (Cetirizine). Some cough mixtures contain antihistamines, e.g. Dimetapp, Demazin.

Oral Steroids (e.g. prednisolone/ redipred) – avoid for 7 days prior to your appointment if safe to do so.

Please DO NOT stop taking your essential medication, especially your asthma medications. Nasal sprays, asthma puffers and antibiotics do NOT interfere with test results. If in doubt, please speak to your GP or give MCPC a call.

On the day of clinic please do not apply steroid creams or moisturisers to forearms.

Note: Skin prick testing will not be performed if there is an increased risk to the patient on the day (e.g. if the child is unwell or has active asthma) or if there are circumstances where the test results would be inaccurate (e.g. if the child has had anaphylaxis in the last 6 weeks or taken antihistamines in the ensuing 5 days or has no skin that is clear of eczema.)

MCPC does not perform oral food challenges, intradermal testing for antibiotic sensitivity or allergy testing for insect venom. If they are needed, the appropriate arrangements will be made.

What to bring to your appointment

If you suspect your child has an allergy to a particular fresh food, please bring it in a sealed container. (Exceptions are egg, milk, soy, wheat, peanut, almond, cashew, hazelnut, walnut, pine nut and sesame. These are stocked items.) For fish and shellfish please provide small (50c sized) cooked and raw samples.

If you have any of the following, please bring:

  • Photos of previous reactions
  • Previous test results
  • Packaging of processed foods to which you believe your child may have reacted. (Packaging contains the list of ingredients.)
  • The names of any medications you are currently taking.

(Please read “Essential preparation for your skin prick test.”)

Useful links

ASCIA (Australian Society for Allergy and Clinical Immunology) is the peak professional body of clinical immunology and allergy in Australia and New Zealand.

Their web site is full of trustworthy, useful information for both patients and health professionals: https://www.allergy.org.au

ASCIA Patients and Consumers home: https://www.allergy.org.au/patients

ASCIA patient information: https://www.allergy.org.au/patients/information

This page includes information on:

    • Allergy and Anaphylaxis
    • Allergic rhinitis (hay fever)
    • Allergy and the skin – including angioedema, eczema and urticaria
    • Allergy prevention – including introduction of solid foods to babies
    • Allergy testing
    • Asthma and allergy, including thunderstorm asthma
    • Food allergy – including information on specific foods
    • Eosinophilic oesophagitis
    • Food intolerance
    • FPIES (Food protein induced enterocolitis syndrome)
    • Insect allergy
    • Medication allergy

 

Anaphylaxis action plans: https://www.allergy.org.au/health-professionals/anaphylaxis-resources/ascia-action-plan-for-anaphylaxis

Other anaphylaxis resources including translations for travel (First Aid Other Languages): https://www.allergy.org.au/health-professionals/anaphylaxis-resources

Epipen –video and written information on how to use EpiPen and EpiPen Jr: https://www.allergy.org.au/health-professionals/anaphylaxis-resources/how-to-give-epipen

ASCIA information for Health Professionals: https://www.allergy.org.au/health-professionals (Includes clinical practice guidelines, action plans, patient information handouts and E-training resources.)

The Royal Children’s Hospital Allergy and Immunology Department has excellent parent information sheets: https://www.rch.org.au/allergy/parent_information_sheets/Parent_Information_Sheets/

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Clayton VIC 3168

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